feat(codex): ship the compaction hook as a plugin-provided hook

The compaction re-injection hook previously required users to hand-merge
an example into user-level ~/.codex/hooks.json — which renders in the
Codex hooks UI as an anonymous, unattributed "Hook 1" and puts the
install burden on every user. Restore the plugin-provided delivery this
repo used before "Remove Codex hooks" (640ce6c0): the Codex manifest
points hooks at hooks/hooks-codex.json, which runs session-start-codex
via ${PLUGIN_ROOT}/hooks/run-hook.cmd with matcher "compact".

Unlike the removed hook, this one never fires at session start — Codex
surfaces skills natively there, which is why the old startup-injecting
hook was removed. The matcher plus the script's own source gate restrict
it to post-compaction re-starts. The explicit manifest pointer also
keeps suppressing Codex's hooks/hooks.json auto-discovery fallback,
which the previous empty-object declaration existed for (7d8d3d4b).

The Codex portal archive now ships hooks/hooks-codex.json,
hooks/run-hook.cmd, and hooks/session-start-codex; other-harness hook
files stay excluded.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

hooks/hooks-codex.json

@@ -2,10 +2,12 @@
   "hooks": {
     "SessionStart": [
       {
+        "matcher": "compact",
         "hooks": [
           {
             "type": "command",
-            "command": "bash \"/ABSOLUTE/PATH/TO/superpowers/hooks/session-start-codex\"",
+            "command": "\"${PLUGIN_ROOT}/hooks/run-hook.cmd\" session-start-codex",
+            "async": false,
             "timeout": 30
           }
         ]