fix(deploy-althing): diff plugin CONTENT, and document the cc channel

The 3.3.0 deploy exposed a false green. `claude plugin update` matches on
the version in plugin.json and declines when it has not moved, so a release
that edits hook or script content without a version bump leaves the Claude
Code cache stale while every version check in this script reports success.
Marketplace and live cache both read 0.1.1, update said "already at the
latest version", and pane-route.sh + README differed.

That particular delta was documentation-only, so nothing was actually
broken — but the script had no way to say so, which is the defect. It now
diffs the marketplace tree against the live cache dir on every run and on
--check, ignoring orphaned version dirs, and says what to do about drift
(bump upstream; never hand-edit Claude Code's bookkeeping).

The 2026-09-01 lesson was "compare the hook list, not the version string".
This is that lesson one turn deeper: the hook list was identical too.

Also documents the cc channel as a deliberately-taken undocumented
interface — expected to break on some future Claude Code release, failing
to pull-only with a logged reason rather than losing mail — and the
herald-before-declare ordering constraint that the script already honours.

scripts/deploy-althing.sh

@@ -50,6 +50,39 @@ market_plugin_version() {
 cache_versions() {
     ls -1 "$HOME/.claude/plugins/cache/althing/althing/" 2>/dev/null | tr '\n' ' ' || echo "absent"
 }
+# ⚠ COMPARE CONTENT, NOT THE VERSION STRING.
+#
+# `claude plugin update` matches on the version in plugin.json and declines
+# when it is unchanged — so a release that edits hook or script CONTENT without
+# bumping the plugin version leaves the Claude Code cache stale while every
+# version check in this script reports success. Measured on the 3.3.0 deploy
+# (2026-09-02): marketplace and cache both read 0.1.1, update said "already at
+# the latest version", and pane-route.sh + README differed. That delta was
+# documentation-only and harmless — the next one need not be.
+#
+# The 2026-09-01 lesson was "compare the hook list, not the version string".
+# This is the same lesson one turn deeper: the hook list was identical too.
+plugin_content_drift() {
+    # Only the cache dir matching the marketplace version is live. Older dirs
+    # carry a .orphaned_at marker and Claude Code no longer loads them; they
+    # differ by construction and saying so every run is noise.
+    local live="$HOME/.claude/plugins/cache/althing/althing/$(market_plugin_version)"
+    local c
+    for c in "$HOME"/.claude/plugins/cache/althing/althing/*/; do
+        [[ -d "$c" && -f "$c/.orphaned_at" ]] && say "  · cache $(basename "$c") orphaned, ignored"
+    done
+    if [[ ! -d "$live" ]]; then
+        say "  ⚠ no cache dir for the marketplace version $(market_plugin_version)"
+        return 1
+    fi
+    if diff -rq --exclude marketplace.json "$MARKET" "$live" >/dev/null 2>&1; then
+        say "  ✓ live cache $(basename "$live") matches the marketplace tree"
+        return 0
+    fi
+    say "  ⚠ live cache $(basename "$live") DIFFERS from the marketplace tree:"
+    diff -rq --exclude marketplace.json "$MARKET" "$live" 2>&1 | sed 's/^/      /'
+    return 1
+}
 
 step "state"
 say "  repo            $(git -C "$REPO" describe --tags --always) $(git -C "$REPO" diff --quiet && echo clean || echo DIRTY)"
@@ -57,6 +90,7 @@ say "  installed tool  $(uv tool list 2>/dev/null | awk '/^althing-core/{print $
 say "  repo plugin     $(repo_plugin_version)"
 say "  marketplace     $(market_plugin_version)"
 say "  CC cache        $(cache_versions)"
+plugin_content_drift || true
 
 if (( CHECK )); then
     say ""
@@ -111,6 +145,15 @@ step "verify"
 say "  installed tool  $(uv tool list 2>/dev/null | awk '/^althing-core/{print $2}')"
 say "  marketplace     $(market_plugin_version)"
 say "  CC cache        $(cache_versions)"
+if ! plugin_content_drift; then
+    say ""
+    say "  ⚠ The cache did NOT take the new plugin content. This happens when the"
+    say "    release changed hook/script content without bumping the plugin version"
+    say "    — `claude plugin update` matches on version and declines. Ask the"
+    say "    althing maintainer for a version bump; do NOT hand-edit the cache or"
+    say "    ~/.claude/plugins/installed_plugins.json, which is Claude Code's own"
+    say "    bookkeeping. Check the diff above for whether it is load-bearing."
+fi
 say "  herald          $(systemctl --user is-active althing-po-herald)"
 say ""
 say "⚠ RESTART Claude Code to load the new plugin hooks. A running session keeps the old ones."