feat(translation): tunable acceptance floor (0.90) + per-post sticky override (#155)

The gate at a fixed 0.80 couldn't catch the real pain: Interpreter (fresh ==
cached, verified by probe) confidently mis-detects short ASCII English like
"... WIP Part 1" as German at 0.86 — above the floor — so it was accepted and a
re-translate reproduced it. Confidence alone can't separate the 0.86 collision
(genuine German lands there too), and single-word mis-flags sit at a confident
1.0 no floor catches.

Two operator-approved levers:

- Acceptance floor is now a live Settings value (ImportSettings.
  translation_min_confidence, default 0.90; surfaced in the Translation card), so
  it's tunable without a redeploy. _accept takes the threshold as a parameter.

- Per-post sticky override (Post.translation_override: auto/force/original).
  'force' stores a translation even below the floor (rescue a skipped
  legit-foreign title); 'original' keeps the original and clears any stored
  translation (kill a confident mis-flag no floor catches). The sweep honors it
  on every run and _reset_translations skips 'original', so the choice survives a
  Re-translate-all. POST /api/posts/<id>/translation-override applies it
  immediately (translate now when the service is up, else queue for the sweep).
  UI: PostTranslationControl on the posts-feed card.

Migration 0084 (both columns + a CHECK on the override). The feed + provenance
serializers expose translation_override.

With a stricter floor the rollback finally works: raise it -> Re-translate all ->
the 0.86 mis-flags are rejected and restored to the original; force /
keep-original handle the residual either way.

Tests: gate thresholds against the param (0.86 rejected at 0.90, explicit-floor
cases); sweep force/original + re-translate-skips-original; override endpoint
(validation, original clears, force queues when disabled, feed exposes it);
settings min_confidence default/save/validate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CgZP9v2otxVJymiYsnVuMy

frontend/src/components/posts/PostCard.vue

@@ -70,6 +70,14 @@
           @click.stop="showOriginal = !showOriginal"
         >{{ showOriginal ? 'Show translation' : `Show original${sourceLangLabel}` }}</button>
 
+        <!-- Per-post translation override (#155): force a skipped translation on,
+             or keep the original for a confidently mis-flagged title. Only where
+             there's text to translate. -->
+        <PostTranslationControl
+          v-if="post.post_title || post.description_plain"
+          :post="post"
+        />
+
         <!-- Faithful (semantic) body render once expanded: backend-sanitized
              HTML (headings, lists, links, inline images). Collapsed and the
              no-detail fallback stay plain text. -->
@@ -136,6 +144,7 @@ import { useModalStore } from '../../stores/modal.js'
 import { usePostsStore } from '../../stores/posts.js'
 import { toPlainText } from '../../utils/htmlSanitize.js'
 import PostSeriesMenu from './PostSeriesMenu.vue'
+import PostTranslationControl from './PostTranslationControl.vue'
 
 const props = defineProps({
   post: { type: Object, required: true },

frontend/src/components/posts/PostTranslationControl.vue

@@ -0,0 +1,102 @@
+<template>
+  <!-- Sticky per-post translation override (#155). Quiet inline control under the
+       post title: force a skipped legit-foreign title on, or knock a wrongly
+       mis-translated one back to the original. The choice sticks through a
+       Re-translate-all. -->
+  <div class="fc-post-tx">
+    <span class="fc-post-tx__label">Translation:</span>
+    <v-menu :disabled="busy">
+      <template #activator="{ props: menuProps }">
+        <button
+          type="button" class="fc-post-tx__btn" v-bind="menuProps" :disabled="busy"
+          :aria-label="`Translation handling: ${currentLabel}`"
+        >
+          {{ currentLabel }}
+          <v-icon size="14">mdi-menu-down</v-icon>
+        </button>
+      </template>
+      <v-list density="compact" min-width="240" class="fc-post-tx__list">
+        <v-list-item
+          v-for="opt in OPTIONS" :key="opt.value"
+          :active="opt.value === current" @click="choose(opt.value)"
+        >
+          <template #prepend>
+            <v-icon size="small">{{ opt.icon }}</v-icon>
+          </template>
+          <v-list-item-title>{{ opt.label }}</v-list-item-title>
+          <v-list-item-subtitle>{{ opt.help }}</v-list-item-subtitle>
+        </v-list-item>
+      </v-list>
+    </v-menu>
+    <v-progress-circular v-if="busy" indeterminate size="13" width="2" />
+  </div>
+</template>
+
+<script setup>
+import { computed, ref } from 'vue'
+
+import { usePostsStore } from '../../stores/posts.js'
+import { toast } from '../../utils/toast.js'
+
+const props = defineProps({ post: { type: Object, required: true } })
+const posts = usePostsStore()
+const busy = ref(false)
+
+const OPTIONS = [
+  { value: 'auto', label: 'Auto', icon: 'mdi-cog-outline',
+    help: 'Translate only when confident enough' },
+  { value: 'force', label: 'Force translate', icon: 'mdi-translate',
+    help: 'Always translate, even at low confidence' },
+  { value: 'original', label: 'Keep original', icon: 'mdi-translate-off',
+    help: 'Never translate — keep the original text' },
+]
+
+const current = computed(() => props.post.translation_override || 'auto')
+const currentLabel = computed(
+  () => (OPTIONS.find((o) => o.value === current.value) || OPTIONS[0]).label,
+)
+
+async function choose (value) {
+  if (value === current.value || busy.value) return
+  busy.value = true
+  try {
+    const res = await posts.applyTranslationOverride(props.post.id, value)
+    if (res.applied === 'queued') {
+      toast({
+        text: 'Saved — this post will translate on the next sweep (service offline).',
+        type: 'info',
+      })
+    }
+  } catch (e) {
+    toast({ text: `Couldn't update translation: ${e.message}`, type: 'error' })
+  } finally {
+    busy.value = false
+  }
+}
+</script>
+
+<style scoped>
+.fc-post-tx {
+  display: inline-flex; align-items: center; gap: 6px;
+  margin: 2px 0 6px;
+}
+.fc-post-tx__label {
+  font-size: 0.72rem;
+  color: rgb(var(--v-theme-on-surface-variant));
+}
+.fc-post-tx__btn {
+  display: inline-flex; align-items: center; gap: 1px;
+  padding: 0; background: none; border: 0; cursor: pointer;
+  font-size: 0.72rem; font-weight: 700;
+  color: rgb(var(--v-theme-on-surface-variant));
+}
+.fc-post-tx__btn:hover { color: rgb(var(--v-theme-accent)); }
+.fc-post-tx__btn:focus-visible {
+  outline: 2px solid rgb(var(--v-theme-accent)); outline-offset: 1px;
+  border-radius: 2px;
+}
+.fc-post-tx__btn:disabled { cursor: default; opacity: 0.6; }
+.fc-post-tx__list :deep(.v-list-item-subtitle) {
+  font-size: 0.7rem;
+}
+</style>

frontend/src/components/settings/TranslationCard.vue

@@ -28,6 +28,21 @@
       @change="onSave"
     />
 
+    <!-- Acceptance floor (#155): latin-script translations below this Interpreter
+         confidence are kept as the original. Per-post overrides handle exceptions. -->
+    <v-text-field
+      v-model.number="minConfidence" label="Acceptance confidence"
+      type="number" min="0" max="1" step="0.01" density="compact"
+      hide-details style="max-width: 200px;" class="mb-1" :disabled="busy"
+      @change="onSaveConfidence"
+    />
+    <div class="fc-muted text-caption mb-3">
+      Latin-script titles Interpreter is less than this sure about (0–1) are kept
+      as the original; CJK is always translated. Default 0.90 — raise it to reject
+      more mis-detections, lower it to translate more. Per-post controls in the
+      posts feed override this either way.
+    </div>
+
     <div class="d-flex align-center flex-wrap mb-3" style="gap: 8px;">
       <v-icon size="12" :color="statusColor">mdi-circle</v-icon>
       <span class="fc-muted text-body-2">{{ statusText }}</span>
@@ -175,6 +190,7 @@ const store = useImportStore()
 const enabled = ref(false)
 const baseUrl = ref('')
 const targetLang = ref('en')
+const minConfidence = ref(0.9)
 const busy = ref(false)
 const running = ref(false)
 const retranslating = ref(false)
@@ -258,6 +274,7 @@ onMounted(async () => {
     enabled.value = !!s.translation_enabled
     baseUrl.value = s.interpreter_base_url || ''
     targetLang.value = s.translation_target_lang || 'en'
+    minConfidence.value = s.translation_min_confidence ?? 0.9
   } catch { /* non-fatal */ }
   await loadStatus()
 })
@@ -282,6 +299,14 @@ async function onSave() {
   })
   await loadStatus()
 }
+async function onSaveConfidence() {
+  // Clamp to [0, 1] so a stray value never bounces off the API 400.
+  let v = Number(minConfidence.value)
+  if (!Number.isFinite(v)) v = 0.9
+  v = Math.min(1, Math.max(0, v))
+  minConfidence.value = v
+  await save({ translation_min_confidence: v })
+}
 async function onRun() {
   running.value = true
   err.value = null

frontend/src/stores/posts.js

@@ -71,6 +71,24 @@ export const usePostsStore = defineStore('posts', () => {
     return await api.get(`/api/posts/${id}`)
   }
 
+  // Set a post's sticky translation override (auto/force/original, #155) and
+  // patch the loaded item in place with the endpoint's result (it translates /
+  // clears immediately when the service is up), so the card reflects the change
+  // without a feed reload.
+  async function applyTranslationOverride(postId, override) {
+    const res = await api.post(`/api/posts/${postId}/translation-override`, {
+      body: { override },
+    })
+    const item = items.value.find((p) => p.id === postId)
+    if (item) {
+      item.translation_override = res.translation_override
+      item.post_title_translated = res.post_title_translated
+      item.description_translated = res.description_translated
+      item.translated_source_lang = res.translated_source_lang
+    }
+    return res
+  }
+
   // Filter overlay for the around/older/newer (in-context anchored)
   // path. Keep this distinct from `filters.value` (the down-only feed)
   // so a normal-feed filter change doesn't leak into an active anchored
@@ -168,7 +186,7 @@ export const usePostsStore = defineStore('posts', () => {
   return {
     items, cursor, loading, done, error, filters,
     cursorOlder, cursorNewer, doneOlder, doneNewer, anchorId,
-    loadInitial, loadMore, getPostFull,
+    loadInitial, loadMore, getPostFull, applyTranslationOverride,
     loadAround, loadOlder, loadNewer,
   }
 })