feat(retro,preamble): gstack-shortcut debt ledger — accepted shortcuts leave a joined trail

When the user accepts an option that is BOTH Completeness <= 7 AND a
durable-scope call, the decision ledger entry (gstack-decision-log, ceiling +
upgrade trigger in the rationale) is the source of truth, and the agent marks
each cut corner in code with gstack-shortcut(dec-<id>): <ceiling>, upgrade
when <trigger> — same edit, no follow-up question, never agent-initiated.

/retro Step 11.5 harvests markers into a debt ledger (grep || true — zero
matches is the healthy case; skill installs and docs excluded), joins on the
decision id so nothing double-counts, tags unlinked and no-trigger rot risks,
and closes with 'N markers, M with no trigger.'

/review suppressions: a marker with ceiling+trigger downgrades a would-be
Completeness Gaps finding to acknowledged debt. Redaction test pins that the
marker ships untouched (the ledger is the point) — it does not match the
TODO(owner) hygiene shape.

Format from dietrichgebert/ponytail's ponytail-debt; store inverted to gstack's
existing decision ledger.

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

review/checklist.md

@@ -180,3 +180,4 @@ the fix, it's ASK.
 - Eval threshold changes (max_actionable, min scores) — these are tuned empirically and change constantly
 - Harmless no-ops (e.g., `.reject` on an element that's never in the array)
 - ANYTHING already addressed in the diff you're reviewing — read the FULL diff before commenting
+- A gap covered by a `gstack-shortcut(dec-*)` marker naming a ceiling and upgrade trigger — that is acknowledged debt with a ledger entry, not a Completeness Gaps finding