desktop: in-app updates, two channels, signed, fed by fixed-tag releases

There was no in-place update anywhere. The app never checked, downloaded or
applied anything, and the only published release predates the whole sync arc —
so `install.sh` would hand out a build with no sync in it. Installing from
per-run CI artifacts, which is what's been happening, is not something an
updater can point at: ephemeral, auth-gated, no stable URL.

Two channels, switchable in the app: `stable` follows tagged releases, `dev`
follows every green push.

The feed is a Fabled-Git release asset, not a ThoughtSync server route. This
reverses the lean recorded in task 1998, and the reason matters — a
server-hosted feed can only reach a desktop that has linked a server, and
local-first-with-no-server is the whole premise. An unlinked install has to be
able to update itself.

Each channel reads a `latest.json` on a release whose TAG NEVER MOVES.
That's forced, not stylistic: Forgejo has no /releases/latest/download/<asset>
route (verified — it 404s with no redirect), so "newest" cannot be named in a
URL. `dev` carries the rolling bundles; `stable` is a pointer release holding
only the manifest, whose URLs aim at the versioned release's assets, so nothing
is duplicated.

The manifest is written by a third job that runs after both bundle jobs. They
build in separate workspaces and neither can see the other's output, but one
manifest has to describe both platforms — generating it inside either job would
silently omit the other, and a missing platform reads to a user as "no update
available" rather than as a broken feed. It reads what actually landed on the
release, so it can never advertise a bundle that failed to upload.

Signing is gated on the secret existing, in the script rather than an `if:`
(the secrets context isn't reliably available to step conditions). No key means
no updater artifacts and no publish: a feed the app would refuse to verify is
worse than no feed, because it looks like it works. CI stays green until the
key lands.

On Linux the updater can only replace an AppImage — a deb or pacman install is
owned by its package manager and must never be overwritten underneath it. The
app detects that case up front and says so, instead of failing halfway through
with a permissions error nobody can read.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SreJkbxB4gx8pPsu8QbLPi

desktop/packaging/write-manifest.sh

@@ -0,0 +1,142 @@
+#!/usr/bin/env bash
+#
+# Write the updater manifest (`latest.json`) for one channel and attach it to that
+# channel's release.
+#
+# WHY A SEPARATE STEP: the Linux and Windows bundles are built by two jobs in two
+# workspaces, and neither can see the other's output — but ONE manifest has to
+# describe both platforms. So this runs after both, reads what actually landed on
+# the release, and writes the manifest from that. Building it inside either job
+# would produce a manifest that silently omits the other platform, and a missing
+# platform reads to a user as "no update available" rather than as a broken feed.
+#
+# WHAT IT READS: the release's own asset list. The signature for each bundle is a
+# `.sig` asset published beside it (see publish-release.sh); its CONTENT is what
+# goes in the manifest, which is why each one is downloaded rather than linked.
+#
+# Tauri's expected shape:
+#   { "version": "0.1.0", "pub_date": "...", "notes": "...",
+#     "platforms": { "<target>-<arch>": { "signature": "...", "url": "..." } } }
+set -euo pipefail
+
+: "${GITHUB_TOKEN:?GITHUB_TOKEN is required}"
+: "${GITHUB_SERVER_URL:?GITHUB_SERVER_URL is required}"
+: "${GITHUB_REPOSITORY:?GITHUB_REPOSITORY is required (owner/repo)}"
+: "${RELEASE_TAG:?RELEASE_TAG is required (the release holding the bundles)}"
+: "${APP_VERSION:?APP_VERSION is required (the version the bundles carry)}"
+
+# Where the manifest is PUBLISHED, which need not be where the bundles live.
+#
+# That split is what makes the stable channel work at all. A versioned release
+# (`v0.2.0`) holds the real assets, but the app can only read a URL that never
+# changes — so the same manifest is also attached to a `stable` release whose tag is
+# permanent and whose only content is this file. It points back at the versioned
+# assets, so nothing is duplicated.
+MANIFEST_TAG="${MANIFEST_TAG:-$RELEASE_TAG}"
+
+API="$GITHUB_SERVER_URL/api/v1/repos/$GITHUB_REPOSITORY"
+AUTH=(-H "Authorization: token $GITHUB_TOKEN")
+NOTES="${RELEASE_NOTES:-}"
+
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT INT TERM
+
+echo "==> Reading assets on release $RELEASE_TAG"
+release="$(curl -sS "${AUTH[@]}" "$API/releases/tags/$RELEASE_TAG")"
+release_id="$(printf '%s' "$release" | grep -oE '"id"[[:space:]]*:[[:space:]]*[0-9]+' | head -1 | grep -oE '[0-9]+')"
+[ -n "$release_id" ] || { echo "ERROR: no release tagged $RELEASE_TAG" >&2; exit 1; }
+assets="$(curl -sS "${AUTH[@]}" "$API/releases/$release_id/assets")"
+
+# Asset names, one per line. The API returns them in a single JSON blob; this is
+# the only field needed, and grep beats adding a jq dependency to the CI image.
+names="$(printf '%s' "$assets" | grep -oE '"name"[[:space:]]*:[[:space:]]*"[^"]+"' | sed -E 's/.*"([^"]+)"$/\1/')"
+
+download_url() { printf '%s/%s/releases/download/%s/%s' "$GITHUB_SERVER_URL" "$GITHUB_REPOSITORY" "$RELEASE_TAG" "$1"; }
+
+# One platform entry, or nothing if that platform's bundle or signature is absent.
+# Emitting a partial entry would be worse than emitting none: the app would try to
+# install something it can't verify.
+platform_entry() {
+  local target="$1" pattern="$2" bundle sig_name
+  bundle="$(printf '%s\n' "$names" | grep -E "$pattern" | head -1 || true)"
+  [ -n "$bundle" ] || { echo "    no bundle matching $pattern — skipping $target" >&2; return; }
+  sig_name="$bundle.sig"
+  if ! printf '%s\n' "$names" | grep -qxF "$sig_name"; then
+    echo "    $bundle has no $sig_name — skipping $target (was the build signed?)" >&2
+    return
+  fi
+  curl -fsSL "${AUTH[@]}" -o "$work/sig" "$(download_url "$sig_name")"
+  # The signature is base64 on one line already; strip any stray newline so it
+  # can't break the JSON string it's about to become.
+  local signature
+  signature="$(tr -d '\r\n' < "$work/sig")"
+  printf '    "%s": { "signature": "%s", "url": "%s" }' "$target" "$signature" "$(download_url "$bundle")"
+}
+
+echo "==> Building the manifest"
+entries=()
+# `.AppImage` only on Linux: the updater replaces the running bundle in place, which
+# a package-manager install (deb/pacman) must never have done to it.
+if entry="$(platform_entry "linux-x86_64" '\.AppImage$')" && [ -n "$entry" ]; then entries+=("$entry"); fi
+if entry="$(platform_entry "windows-x86_64" '\.exe$')" && [ -n "$entry" ]; then entries+=("$entry"); fi
+
+if [ ${#entries[@]} -eq 0 ]; then
+  echo "ERROR: no signed bundle on $RELEASE_TAG — refusing to publish an empty manifest." >&2
+  echo "       (An empty manifest would tell every client it is up to date.)" >&2
+  exit 1
+fi
+
+# No `date -u -Is` — busybox date in the CI image doesn't take it.
+pub_date="$(date -u '+%Y-%m-%dT%H:%M:%SZ')"
+{
+  printf '{\n'
+  printf '  "version": "%s",\n' "$APP_VERSION"
+  printf '  "pub_date": "%s",\n' "$pub_date"
+  printf '  "notes": "%s",\n' "$NOTES"
+  printf '  "platforms": {\n'
+  for i in "${!entries[@]}"; do
+    [ "$i" -eq 0 ] || printf ',\n'
+    printf '%s' "${entries[$i]}"
+  done
+  printf '\n  }\n'
+  printf '}\n'
+} > "$work/latest.json"
+
+echo "==> Manifest:"
+cat "$work/latest.json"
+
+# --- resolve the release the manifest is published TO ------------------------
+if [ "$MANIFEST_TAG" = "$RELEASE_TAG" ]; then
+  target_id="$release_id"
+  target_assets="$assets"
+else
+  echo "==> Resolving the $MANIFEST_TAG channel release"
+  target="$(curl -sS "${AUTH[@]}" "$API/releases/tags/$MANIFEST_TAG")"
+  target_id="$(printf '%s' "$target" | grep -oE '"id"[[:space:]]*:[[:space:]]*[0-9]+' | head -1 | grep -oE '[0-9]+' || true)"
+  if [ -z "${target_id:-}" ]; then
+    # First publish to this channel. A pointer release: no bundles of its own, just
+    # a permanent tag for the manifest to live under.
+    echo "    creating it (pointer release, manifest only)"
+    body="{\"tag_name\":\"$MANIFEST_TAG\",\"name\":\"ThoughtSync ($MANIFEST_TAG channel)\",\"draft\":false,\"prerelease\":false,\"body\":\"Update channel pointer. The installable builds live on the versioned releases; this holds only the updater manifest.\"}"
+    target="$(curl -sS -X POST "${AUTH[@]}" -H "Content-Type: application/json" -d "$body" "$API/releases")"
+    target_id="$(printf '%s' "$target" | grep -oE '"id"[[:space:]]*:[[:space:]]*[0-9]+' | head -1 | grep -oE '[0-9]+')"
+  fi
+  [ -n "${target_id:-}" ] || { echo "ERROR: could not resolve the $MANIFEST_TAG release" >&2; exit 1; }
+  target_assets="$(curl -sS "${AUTH[@]}" "$API/releases/$target_id/assets")"
+fi
+
+# Replace rather than duplicate: Forgejo rejects a second asset with the same name,
+# and this file is rewritten on every publish by design.
+old_id="$(printf '%s' "$target_assets" \
+  | grep -oE "\"id\"[[:space:]]*:[[:space:]]*[0-9]+[^}]*\"name\"[[:space:]]*:[[:space:]]*\"latest\.json\"" \
+  | head -1 | grep -oE '[0-9]+' | head -1 || true)"
+if [ -n "${old_id:-}" ]; then
+  echo "==> Removing the previous latest.json (id $old_id)"
+  curl -fsS -X DELETE "${AUTH[@]}" "$API/releases/$target_id/assets/$old_id" >/dev/null
+fi
+
+echo "==> Uploading latest.json to $MANIFEST_TAG"
+curl -fsS -X POST "${AUTH[@]}" "$API/releases/$target_id/assets?name=latest.json" \
+  -F "attachment=@$work/latest.json" >/dev/null
+
+echo "==> Done. $MANIFEST_TAG now advertises $APP_VERSION for ${#entries[@]} platform(s)."