feat(primer): broaden Codex alignment hold to all real consumers; pre+post slot window

Address review gaps in the primer-alignment hold so the fixed-slot primer
reliably wins the first-request race for the shared Codex window:

- Extract the time-based hold into a dependency-free leaf module
  (codex-primer-alignment.ts) so every Codex path can share it without import
  cycles.
- Add a pre-slot hold window (2 min) in addition to the post-slot (5 min) and
  the 04-08 KST dawn gap, closing the "request a beat before the slot" gap.
- Hold the dashboard's periodic Codex warm-up too: runCodexWarmupCycle now
  skips during the hold unless called with isPrimer (the scheduled primer sets
  it), so the warm-up can't anchor the window ahead of the primer.
- Remove the urgent @-mention bypass on the reviewer/arbiter and owner holds —
  the reset is anchored unconditionally as requested.
- Reviewer/arbiter hold resumes exactly once after the window via the existing
  per-revision claim (poll re-detect; no double run).

Note: the unified lease boundary (syncHostCodexSessionFiles) is synchronous and
throws a terminal "Codex unavailable", so it can't host a clean defer+resume;
gating stays at the async turn-scheduling layer that can re-queue. Honest caveat
unchanged: making the primer first is necessary but not sufficient to pin a
trailing reset.

Verified: typecheck, build, bundle-smoke; full suite 1482 passing with only the
9 pre-existing env-config baseline failures (service-routing/paired-context/
migrate-room owner=claude vs codex-main); new alignment + warmup-hold tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/codex-warmup.ts

@@ -5,6 +5,7 @@ import os from 'os';
 import path from 'path';
 import { fileURLToPath } from 'url';
 
+import { shouldHoldCodexForPrimerAlignment } from './codex-primer-alignment.js';
 import { DATA_DIR } from './config.js';
 import type { AppConfig } from './config/schema.js';
 import {
@@ -36,6 +37,13 @@ interface CodexWarmupRuntimeOptions {
   statePath?: string;
   shouldSkip?: () => boolean;
   ignoreZeroUsageWindow?: boolean;
+  /**
+   * Set by the scheduled usage primer so its call is exempt from the
+   * primer-alignment hold. Any other warm-up caller (e.g. the dashboard's
+   * periodic warm-up) is held during the slot windows so it can't anchor the
+   * shared Codex window ahead of the primer.
+   */
+  isPrimer?: boolean;
 }
 
 export type CodexWarmupCycleResult =
@@ -317,6 +325,12 @@ export async function runCodexWarmupCycle(
     return { status: 'skipped', reason: 'runtime_busy' };
 
   const nowMs = runtime.nowMs ?? Date.now();
+  // Hold every non-primer warm-up during the slot windows so it can't anchor
+  // the shared Codex 5h window ahead of the scheduled primer (which passes
+  // isPrimer). Skipping is safe — a warm-up is best-effort.
+  if (!runtime.isPrimer && shouldHoldCodexForPrimerAlignment(nowMs)) {
+    return { status: 'skipped', reason: 'primer_alignment_hold' };
+  }
   const nowIso = new Date(nowMs).toISOString();
   const statePath = runtime.statePath ?? DEFAULT_STATE_FILE;
   const state = readWarmupState(statePath);