feat(desktop): unify assistant dock — kimi web + companion tabs, retire surface mounts

[agentfleets]

Motivation

User-approved redesign: the dock IS the companion. The app-level assistant dock (kimi web) and the per-surface AgentCompanion panels (Read's aside + reader tab, Author's aside) were two homes for "talk to an agent" — the companion even duplicated the dock's panel shape. This unifies them: the assistant dock becomes a tabbed panel — kimi web | Companion — hosting the ONE AgentCompanion, and the per-surface mounts retire. The kimi-web lifecycle (daemon hold, detach/attach, confirmed close) is untouched and stays scoped to the kimi tab.

This is also the SurfaceContext contract the design review asked for (docs/discussions/desktop-design-review.md §4): surfaces declare "what am I looking at" + "what can you insert" through a small registry instead of hand-rolled per-mount props.

Design

1. Tabbed dock. state/assistant.ts gains view: 'kimi' | 'companion', persisted like dockSide (termipod.assistant.view). AssistantDock.tsx's header leads with a segmented tab strip (the existing .seg/.seg-btn idiom). The body renders BOTH the kimi WebPanel and one AgentCompanion, each CSS-hidden by view (visibility, never unmounted once started — the webview white-screen hazard applies, so no display:none). Detach/attach, the placeholder, and the confirmed close behave exactly as before, on the kimi tab only; the Companion tab stays usable while kimi is detached.

2. Context-provider registry — new state/companionContext.ts (zustand). Surfaces register { label, build, insert? } keyed by job; registration marks the job most-recently-focused (a simple focus-order stack), unregistration removes it. The dock companion reads the ACTIVE provider for its context chip + onInsert.

• ReadSurface registers the selected paper: label = title, build = the Paper/Authors/Year/Abstract block the aside passed, insert = append to the ref's notes.
• AuthorSurface registers the active document: the exact three-branch build() the aside passed (markdown draft / figure spec / other-kind one-liner), insert = append into the markdown draft, or replace the figure body with the unfenced reply (today's semantics preserved for both kinds; structured bodies register no insert).
• Focus-tracking approximation (sanctioned by the design): Read/Author have no focus event, so a surface registers on mount + selection/active-document change and unregisters on unmount/no-context. build/insert read their stores LIVE at call time, so registration only refires on label-affecting changes, not per keystroke.

3. Dock companion instance. storageKey: 'termipod.dock.agent' with a one-time, read-only fallback to the retired mounts' keys (termipod.read.agent, then termipod.author.agent) so existing agent bindings survive — state/companionBinding.ts. Everything else the component already does (agent picker, hub/local toggle, @-mention, annotate button, D2.1 annotationTargets self-registration, image handoff) is unchanged.

4. Retired. The Read aside + embedded reader assistant tab, the Author aside, both "✦ Assistant" toolbar buttons, showAgent/agentW state + resize handles, dead CSS (.read-agent, .author-agent, .ref-assistant-body), and the author.assistant / author.assistantHint / read.tabAssistant i18n keys (en+zh). New keys: assistant.tabKimi, assistant.tabCompanion (en+zh).

5. Amendment — kimi attach availability + reveal. The annotation target row's kimi availability moves from open && !detached to started && !detached (guest mounted = attachable — a hidden dock's guest never unmounts). On a successful kimi attach — injected OR clipboard fallback — the dock auto-opens on the kimi tab (reveal('kimi')) so the user lands in kimi's composer to review and send.

6. Amendment — dock steps aside during selection. While the overlay is armed (any origin: companion compose button, status-bar chip, palette, hotkey — all funnel through arm()), the dock hides via an annotating CSS class driven by dockHiddenForPhase(phase) — open is never flipped, so Esc/cancel restores it exactly as it was, and it stays out of the captured pixels. On target pick the dock returns revealed: kimi tab after a kimi attach, Companion tab after a companion handoff — including the compose-box-armed case (the dock companion's own annotate button).

7. Handoff reveal. handOffToCompanion reveals the dock on the Companion tab when the handoff targets the dock companion's key (handoffRevealsDock) — and since reveal sets started, this also mounts the dock+companion on a never-opened dock, so the crop chip has somewhere to land.

The pure decisions (dock-hide flag, handoff routing, reveal predicate) live in bridge-free state/annotationTargets.ts per the established pattern (the store imports the shell bridge, which node ESM can't resolve).

Tests

• New unit (node --test, desktop): assistant.test.ts (view persistence/switching, reveal, kimiAttachable truth table), companionContext.test.ts (register/replace/focus-order/unregister/insert passthrough), companionBinding.test.ts (the dock-key fallback migration incl. priority + non-dock no-fallback), annotation.test.ts (annotating-hide flag, handoff routing/reveal contract). annotationTargets.test.ts fixtures moved off the retired storage keys.
• E2E (desktop/electron/e2e/annotation.spec.ts): the D2 test now opens the dock from the status-bar chip and drives the Companion tab (the old flow clicked the retired "✦ Assistant" button); both tests additionally assert the dock hides while armed and reveals on the Companion tab after the handoff. CI is the e2e gate; the spec stays hermetic (TERMIPOD_E2E, throwaway user-data-dir + workspace).

Verification

• desktop: npm run build (tsc --noEmit + vite) — green
• desktop/electron: npx tsc --noEmit — green; npm test — 262/262 pass
• desktop: node --test 'src/**/*.test.ts' — 445/445 pass (32 in the new/updated files)
• scripts/lint-desktop-tokens.sh — clean (semantic tokens only, no raw hex, no phantom var(--*))
• scripts/lint-docs.sh — clean; no doc changes (docs referencing AgentCompanion are design-history plan/discussion docs, and the design-review doc already advocates this contract)

Notes

• kimiweb (the embedded kimi web panel, its server lifecycle, detach window) is untouched.
• The termipod.read.reader.agent reader-tab binding is deliberately not migrated — it was a second, reader-scoped binding, not a primary one.