v0.51.23 — Release A: 7-PR contributor batch

Theme: Stale-cleanup pending-turn preservation + title refresh marker persistence + Japanese i18n refresh + Kanban predicate hardening + cron edit snapshot fix + workspace heading affordance polish.

Constituent PRs

• #1856 by @ai-ag2026 — Materialize a pending user turn before stale stream cleanup
• #1859 by @ai-ag2026 — Persist llm_title_generated marker through Session round-trip
• #1863 by @koshikai — Refresh Japanese (ja) locale bundle (108/-108 i18n keys)
• #1869 by @franksong2702 — Parametrize Kanban double-404 test across HTTP methods (closes #1845)
• #1870 by @franksong2702 — Tighten Kanban stale-client predicate (closes #1839)
• #1871 by @franksong2702 — Fix cron edit snapshot source for no-agent saves (closes #1840)
• #1872 by @franksong2702 — Disable workspace heading affordance when no workspace registered (closes #1842)

Pre-release verification

• Full pytest under HERMES_HOME isolation: 4819 passed, 8 skipped, 1 xfailed, 2 xpassed, 8 subtests passed in 150.85s on Python 3.13.
• Browser API harness (run-browser-tests.sh against stage-318 on port 8789): all 11 checks PASS.
• node -c on static/i18n.js, static/panels.js, static/ui.js: clean.
• Stage diff: 14 files, +251/-124.
• Opus advisor pass on stage-318 brief: SHIP with two release-note items incorporated. No MUST-FIX.
• Pre-stamp re-fetch of all 7 PR heads: no contributor force-pushes during the Opus window.

Test count

4817 → 4830 collected, 4819 passing (+13 net new tests).

Closes

• #1839 (PR #1870)
• #1840 (PR #1871)
• #1842 (PR #1872)
• #1845 (PR #1869)

Closes #1856, #1859, #1863, #1869, #1870, #1871, #1872.