ci(extension): shadow the derived version + verify real XPI contents

Milestone #271 steps 2 and 3. Neither changes what gets published.

STEP 2 -- shadow mode.

build.yml's sign-extension and ci.yml's extension-version guard now log the
version that WOULD be derived from git history alongside the hand-maintained
one. Nothing reads the derived value, and neither site can fail because of it.

This exists because `web-ext sign` is one-shot per version: AMO 409s on a
repeat, so a wrong formula burns a real version number that cannot be
reclaimed. Comparing the two across real builds is the only way to validate it
at zero cost. sign-extension runs on main only, so main pushes are the sole
source of truth for whether the derived number moves exactly when the shipped
extension changes -- the dev-side log is a convenience, not the evidence.

sign-extension now checks out with fetch-depth: 0. The derived version is a
commit count and a depth-1 clone cannot produce one.

STEP 3 -- XPI content verification.

Every other packaging assertion checks our declaration against itself. This is
the first that asks web-ext what it ACTUALLY wrote into the archive.

That assumption was both unverified and fragile: `test/**` only survives to
web-ext because callers `set -f` before substituting it, so losing that
quoting would silently start shipping dev files with no other signal. The step
builds the XPI and asserts test/, scripts/, vitest.config.js, package.json,
package-lock.json, README.md and node_modules are absent -- and, because an
over-matching exclusion would break the extension at runtime rather than at
build time, that manifest.json, all four lib/*.js and every UI directory are
present.

unzip is installed only when missing; node:24-bookworm-slim may not carry it.

Refs #2399, #2400

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

.forgejo/workflows/extension.yml

@@ -38,3 +38,45 @@ jobs:
       # package version-consistency checks. No browser, no network.
       - name: Unit tests
         run: cd extension && npm run test:unit
+
+      # Everything else about packaging is asserted against our own declaration
+      # of what ships. This is the only check that asks web-ext what it ACTUALLY
+      # put in the archive. Until now that was an unverified assumption about
+      # glob semantics — and a fragile one: `test/**` reaches web-ext intact
+      # only because callers `set -f` first, so losing that quoting would
+      # silently start shipping dev files with no other signal.
+      - name: Verify XPI contents
+        run: |
+          set -eu
+          command -v unzip >/dev/null 2>&1 || { apt-get update -qq && apt-get install -y -qq unzip; }
+          cd extension
+          npm run build
+          ZIP=$(ls web-ext-artifacts/*.zip | head -1)
+          echo "=== packaged entries in $ZIP ==="
+          unzip -Z1 "$ZIP" | sort
+          echo "=== end ==="
+          ENTRIES=$(unzip -Z1 "$ZIP")
+          fail=0
+          # Must NOT ship: repo infrastructure with no business in a user's browser.
+          for pat in 'test/' 'scripts/' 'vitest.config.js' 'package.json' 'package-lock.json' 'README.md' 'node_modules/' 'web-ext-artifacts/'; do
+            if echo "$ENTRIES" | grep -q "^$pat"; then
+              echo "ERROR: '$pat' was packaged into the XPI but must not be"
+              fail=1
+            fi
+          done
+          # Must ship: if an exclusion pattern ever over-matches, the extension
+          # breaks at runtime rather than at build time, so assert presence too.
+          for req in 'manifest.json' 'lib/url.js' 'lib/api.js' 'lib/platforms.js' 'lib/cookies.js'; do
+            if ! echo "$ENTRIES" | grep -q "^$req$"; then
+              echo "ERROR: '$req' is missing from the XPI"
+              fail=1
+            fi
+          done
+          for dir in 'background/' 'popup/' 'options/' 'content/' 'icons/'; do
+            if ! echo "$ENTRIES" | grep -q "^$dir"; then
+              echo "ERROR: nothing from '$dir' was packaged"
+              fail=1
+            fi
+          done
+          [ "$fail" -eq 0 ] || exit 1
+          echo "XPI contents verified."