feat(sentry): add the sentry overnight-hygiene engine workflow

Phase 2 of the sentry supervisor. sentry.org is the engine: an interval loop (default hourly) that walks a fixed pass list (roam pull, inbox zero, triage, todo cleanup, task audit, working-files hygiene, spec board, link integrity, git health, prep freshness) and commits each writing pass to a throwaway sentry/<date>-<host> branch. Nothing pushes. The morning teardown (review, squash-merge, delete) stays Craig's.

The file owns the whole engine: the :COMMIT_AUTONOMY: entry ticket, the interactive entry gates (clean tree, green suite, prior-branch check, ff-only reconcile) that run with Craig present, the single-runner and roam-write locks via agent-lock, the probe-work-session-context-commit pass contract, the digest and morning-approval queue, the skip-not-degrade safety model, the conditional fire-end suite, the multi-day stall notification, and the stop-sentry shutdown.

Every one of the spec's ten decisions and twelve review findings is reflected: host-suffixed branch so the two daily drivers don't collide, tmpfs lock homes so a lock never rides roam-sync to the other machine, roam-sync kept as the roam repo's only committer, spine-excluded dirty checks so sentry's own bookkeeping can't trip its safety skip, and the queue-don't-execute rule for every judgment or destructive action.

Phase 3 wires the roam writers (inbox.org, knowledge-base.md) to acquire the roam-write lock and adds the wrap-it-up guard. Until then the engine is documented but the companions don't yet cooperate. INDEX.org lists it under Tasks and planning.

1 files changed, 3 insertions, 0 deletions

diff --git a/.ai/workflows/INDEX.org b/.ai/workflows/INDEX.org
index b031dbe..02c4264 100644
--- a/.ai/workflows/INDEX.org
+++ b/.ai/workflows/INDEX.org
@@ -58,6 +58,9 @@ This index must list every =.org= file in =.ai/workflows/= except this one and e
   - Speedrun triggers: "speedrun", "no approvals speedrun", "speedrun these: <task set>" — any phrase containing "speedrun" routes here (the preset), never to =no-approvals.org=
   - Manual triggers: "work the backlog", "work the backlog with <task set>" (file-only defaults)
   - Synthesis trigger: "synthesize backlog metrics" — read the per-project metrics logs, compute trends + the corrections signal, write one =:agent:metrics:= KB node (personal projects only)
+- =sentry.org= — the overnight hygiene supervisor: an interval loop (default hourly) that walks a fixed pass list (roam pull, inbox zero, triage, todo cleanup, task audit, working-files hygiene, spec board, link integrity, git health, prep freshness), commits each writing pass to a throwaway =sentry/<date>-<host>= branch (never pushed), and parks every judgment call and destructive action in a morning-approval queue. Gated on =:COMMIT_AUTONOMY: yes= plus interactive entry gates (clean tree, green suite) with Craig present. Locks via =agent-lock=; morning teardown (review, squash-merge, delete) is Craig's, never automated.
+  - Triggers: "start sentry", "run sentry", "arm sentry", "sentry mode", "start sentry every <interval>"
+  - Stop trigger: "stop sentry", "stand down sentry", "sentry off"
 
 ** Calendar