v0.51.24 — Release B: 5-PR contributor batch

Theme: Local-server custom-provider model preservation + oversized upload preflight + ai-gateway phantom Custom group fix + Kanban lifecycle controls + cross-container gateway liveness.

Constituent PRs

• #1862 by @franksong2702 — Preserve slashed model ids for custom:<local-server> providers (closes #1830)
• #1868 by @franksong2702 — Browser-side oversized upload preflight check (closes #1867)
• #1883 by @Sanjays2402 — Fix phantom duplicate Custom group when active provider is ai-gateway (closes #1881)
• #1886 by @franksong2702 — Kanban lifecycle controls: remove unsafe Start/Running, rename Nudge→Preview, empty-board guidance (closes #1885)
• #1887 by @Sanjays2402 — Cross-container gateway liveness via state-file freshness fallback (closes #1879)

Pre-release verification

• Full pytest under HERMES_HOME isolation: 4847 passed, 8 skipped, 1 xfailed, 2 xpassed, 8 subtests passed in 142.86s on Python 3.11.
• Browser API harness (port 8789): all 11 checks PASS.
• node -c on static/i18n.js, static/panels.js, static/ui.js: clean.
• Stage diff: 11 files, +849/-43.
• Opus advisor pass on stage-319: SHIP with one non-blocking flag. No MUST-FIX.
• Pre-stamp re-fetch of all 5 PR heads: no contributor force-pushes during the Opus window.

Mid-stage maintainer notes

#1886 was based on pre-v0.51.23 master, so during stage rebase the maintainer:

1. Resolved CHANGELOG.md conflict (accept master).
2. Merged i18n.js with v0.51.23's Japanese refresh (translated kanban_work_queue_hint for ja).
3. Restored two silent reverts from #1886's stale-base diff: #1872's static/index.html workspace-heading change, and #1871's static/panels.js:837 _cronPreFormDetail reference.

Both restorations verified by Opus against post-merge stage. All 4847 tests pass.

Test count

4830 → 4858 collected, 4847 passing (+28 net new tests).

Closes

• #1830 (PR #1862)
• #1867 (PR #1868)
• #1879 (PR #1887)
• #1881 (PR #1883)
• #1885 (PR #1886)

Closes #1862, #1868, #1883, #1886, #1887.