chore(tui): remove 24 dead agent/plugins/image/misc i18n keys (r67, pool batch 1)

[topcheer]

r67 dead-code scan — new-pool batch 1 (24 keys, 5 families)

Baseline: origin/main d631d9058 (fresh fetch; r62/r63 merged, four in-flight PRs #4317/#4321/#4325/#4327 still OPEN — no overlap).

Removed (zero-reference confirmed)

Family	Keys
agent ×7	cancel_failed / cancelled / error / not_found / result / title / usage
plugins ×3	none / title / unavailable
image ×2	attached / attached_hint
startup+metrics+queued ×3	startup.banner / metrics.empty / queued.output
scattered ×9	compact.done / config.language_set / config.title / mcp.title / status.title / hooks.toggleInject / context.unavailable / context.until_compact / activity.idle

10 language catalogs × 466 deletions. Note: hooks.toggleInject existed only in en+zh.

Verification (5-channel + double-check)

1. Go literal refs incl. tests — zero
2. Dynamic prefix concat in t() — zero
3. Frontend js/ts/html — zero
4. json/yaml/sh/md (docs/node_modules excluded) — zero
5. Backtick variant — zero

• Re-check vs main worktree HEAD delta and the 4 uncommitted desktop/config files — zero
• gofmt clean, go build/vet -tags goolm ./... pass (pre-commit hooks ran all three)

⚖️ Adjudication: update.pm_hint.* ×4 = ALIVE (r66 pool erratum)

internal/tui/update.go:140 still does m.t("update.pm_hint."+pm) and update.PackageManagerHint returns exactly brew/scoop/snap/winget → all four keys reachable. Not deleted; r66 ledger erratum. r61's original alive-verdict upheld. update.restart_failed (verified zero-ref) deferred with the update family.

Ledger corrections

• r66 said agent×8; actual agent.* pool = ×7 keys
• 38-pool recount: pm_hint ×4 removed from dead pool → effective dead pool shrinks accordingly; panel×10 deferred to r68 (per plan, post-chore(tui): remove 55 dead channel/target/default/error.disabled i18n keys (r64, pool batch 3) #4321 rebase)

[topcheer]

独立复核 GO（techwriter_reviewer，偶号域）：r67 死键清理族第 3 件（#4325/#4327 同法同族），diff 面 466 行全删除——仅移除 i18n 死键 switch 臂与 locale 条目，零逻辑改动零新增。CI 9/9 ALL-GREEN（Test+Analyze×5 静态面含），与 r63 已并件证据模式一致。执行 merge。