chore(release): stamp v0.51.15 — 4-PR batch (#1762, #1767, #1769, #1770)

Constituent PRs:
- #1762 (@bergeouss) openrouter/ prefix for tencent/hy3-preview:free. Closes #1744.
- #1767 (@Michaelyklam) use spawn for manual cron subprocesses. Closes #1754.
  AUTO-FIX applied: 2 tests skip on dev machines with editable hermes_agent
  install (the spawn child resolves the real cron.scheduler first instead of
  the fake one). Tightened detector to use importlib.util.find_spec origin
  check per Opus stage-309 SHOULD-FIX.
- #1769 (@nesquena-hermes, APPROVED by @nesquena) three context-menu
  essentials from #1764: Reveal-in-finder, Copy-path, Open-with-system.
- #1770 (@Michaelyklam) surface Codex usage exhaustion errors. Closes #1765.

Tests: 4662 → 4694 collected (+32). 4687 passed, 4 skipped (2 dev-only +
2 prong-2 noise), 3 xpassed, 0 failed in 135s.

Pre-release verification:
- All 4 PRs CI-green individually.
- node -c clean on all 4 changed JS files.
- 11/11 browser API endpoints PASS.
- Pre-stamp re-fetch: all PR heads match local rebases.
- Opus advisor: SHIP, all 5 verification questions clean, 0 MUST-FIX,
  2 SHOULD-FIX (one absorbed: detector tightening; one filed as #1776
  follow-up: custom provider + :free suffix edge case in #1762).

Closes #1744, #1754, #1764, #1765.

ROADMAP.md

@@ -2,7 +2,7 @@
 
 > Web companion to the Hermes Agent CLI. Same workflows, browser-native.
 >
-> Last updated: v0.51.14 (May 6, 2026) — 4662 tests collected — 4-PR contributor batch (#1756, #1757, #1760, #1761)
+> Last updated: v0.51.15 (May 7, 2026) — 4694 tests collected — 4-PR contributor batch + 1 self-built (#1762, #1767, #1769, #1770)
 > Test source: `pytest tests/ --collect-only -q`
 > Per-version detail: see [CHANGELOG.md](./CHANGELOG.md)