feat(410): the Claude Code plugin becomes a thin adapter (#4031)

Step 4 of milestone 410 "One owner per piece of guidance". The plugin's
static session context was a second copy of using-scribe and the server
index. It now says only what Claude Code needs said: 8,705 -> 1,791 chars.

scribe_static_context.md:
- points at using-scribe for how to work with Scribe, and names the process
  skills
- Claude Code specifics: keep one copy in Scribe rather than CLAUDE.md or
  auto-memory (leave auto-memory at its default); injected lines are
  retrieval, not the whole set; compact at clean seams; stored Processes
  arrive as scribe-proc-* skills with /scribe:sync; say so when the tools
  are unavailable
- retired: the restated reflexes, "how the surfaces divide the work", and
  the "follow the surface that assumes least" precedence (decision #4027)

Hook behaviour is unchanged. The SessionStart hook header says what the
static tier now carries, and the unreachable-instance status points at the
using-scribe skill instead of "the standing guidance above".

README and manifest describe the plugin as the Claude Code adapter over the
shared, client-neutral skills. Fixed along the way: the README said the
SessionStart hook "injects your rules" and suggested disabling auto-memory,
both contradicting the product since milestone 394.

Tests: the session-start rules guards now pin the owner (using-scribe) and
the index (_INSTRUCTIONS) rather than every surface; the Systems-reflex and
snippet-trigger guards pin their owners; the reporting-reflex guard pins
using-scribe. The loss guard and client-neutral guard stay green. Plugin
version minted.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

plugin/hooks/scribe_session_context.sh

@@ -1,11 +1,12 @@
 #!/usr/bin/env bash
 # Scribe plugin — SessionStart push channel (two tiers + compaction re-grounding).
 #
-# Tier 1 (STATIC, always fires, no auth, no network): injects a bundled
-# behavioral mandate (scribe_static_context.md) so a fresh session knows to
-# reach for Scribe — record work, recall before acting — even when the instance
-# is unreachable or unconfigured. The static tier is the load-bearing floor that
-# does not depend on the key or the network.
+# Tier 1 (STATIC, always fires, no auth, no network): injects the Claude Code
+# adapter's own guidance (scribe_static_context.md) — where Scribe's reflexes
+# are stated (the using-scribe skill), Claude Code's memory files, /compact,
+# /scribe:sync, and what to do when Scribe is unavailable. Since milestone 410
+# (decision #4027) it carries only what this client needs said; the reflexes
+# themselves are owned by the shared skills and the server's index.
 #
 # Tier 2 (DYNAMIC, best-effort enrichment): curls the operator's Scribe instance
 # for active-project context and appends it. Config comes from
@@ -160,7 +161,7 @@ if [ -n "$url" ] && [ -n "$token" ] && command -v curl >/dev/null 2>&1; then
   # (milestone 394). Nothing is preloaded, so there is no set whose
   # drift a later write could be told about — a rule is retrieved at
   # the moment it applies, which cannot be stale.
-  [ -z "$dyn" ] && status="> ⚠️ Scribe: live project context could not be loaded this session (instance unreachable or request failed). The standing guidance above still applies — ask for rules with \`search(content_type=\"rule\")\` and project context with \`enter_project()\` as needed."
+  [ -z "$dyn" ] && status="> ⚠️ Scribe: live project context could not be loaded this session (instance unreachable or request failed). The using-scribe skill still applies — ask for rules with \`search(content_type=\"rule\")\` and project context with \`enter_project()\` as needed."
 elif [ -n "$url" ] && [ -z "$token" ]; then
   status="> ⚠️ Scribe: live context disabled this session — the API key is not configured (Scribe base URL is). Set it with \`/plugin\` → Scribe → configure, or export SCRIBE_TOKEN. Tools still work; ask for rules with \`search(content_type=\"rule\")\` and project context with \`enter_project()\`."
 elif [ -z "$url" ] && [ -z "$token" ]; then