[twarp 07b] Claude Code panel: resurrect view + event model

[timomak]

twarp 07b — Claude Code panel: resurrect view + event model

First implementation sub-phase of feature 07 (roadmap/07-claude-code-panel/). Specs (PRODUCT.md + TECH.md) merged in #66.

Framing: feature 02 removed Warp's AI service (accounts, LLM clients, billing, cloud storage). Feature 07 brings back only the rendering layer, driven by the local claude CLI the user already runs. 7b is the scaffold — the panel registers, opens, and renders its zero/unavailable states. It spawns no claude process; the live session is 7c. No LLM client, billing, or cloud sync comes back.

What's in this PR

• crates/claude_code (new, headless): the contract both halves of the feature meet at — the thin twarp-native TranscriptEvent the 7c driver will emit and the Transcript / TranscriptItem model the panel renders. Transcript::apply (delta accumulation, in-place TodoWrite updates, tool-result matching, verbatim error surfacing) is unit-tested (6 tests) with no GPUI, per TECH §Parallelization. The subprocess + stream-json parser land in 7c.
• app/src/claude_code_panel/ (new): a child View (the Warp Drive pattern, so 7c–7h have a home). Renders the zero state (explanation + message input + "Start session", PRODUCT §5) or, when claude is not on PATH, the unavailable state (PRODUCT §6, re-checked each render). The input is a styled, non-editable placeholder in 7b; real editing is 7c/7g.
• Registration: ToolPanelView::ClaudeCode + LeftPanelDisplayedTab::ClaudeCode (both From directions), toolbelt button (Agent Mode icon), focus/render arms, and a compute_left_panel_views push gated on the new FeatureFlag::ClaudeCodePanel.
• Feature flag (dogfood-only): FeatureFlag::ClaudeCodePanel in DOGFOOD_FLAGS + cargo feature claude_code_panel, intentionally absent from default so it stays hidden in stable.
• Keybinding ⌘⌥K (Ctrl+Alt+K): WorkspaceAction::ToggleClaudeCodePanel + CustomAction::ToggleClaudeCodePanel. The default chord is registered in custom_tag_to_keystroke, not EditableBinding::with_key_binding — the feature-06 lesson (it would clobber Trigger::Custom and panic the mac menu). The binding stays an EditableBinding, so it remains remappable. Conflict check: cmd-alt-k / ctrl-alt-k were unbound. Per PRODUCT §2, re-pressing the chord while the tab is active returns focus to the terminal rather than collapsing the whole left panel.

Deferred to later sub-phases (so review scopes correctly)

• 7c: spawn claude, stream assistant text, send messages, Stop/teardown, UniformList bottom-stick auto-scroll, markdown, cwd-in-header (§8–§22, §52–§57). The transcript renderer here is a placeholder.
• 7d–7f: rich tool cards, diff cards, thinking blocks, in-place todo list (§23–§38).
• 7g: permission prompts + permission-mode selector + editable multi-line input (§39–§45).
• 7h: session list + resume + the zero-state "Resume…" entry point (§46–§51).

Validation

• cargo check and cargo clippy clean with --features claude_code_panel; rustfmt clean; claude_code unit tests pass (6/6).
• Built warp-oss --features claude_code_panel and launched it: app reaches steady state with no startup panic (the menu-build path the feature-06 keybinding bug tripped). claude_code_panel adds no menu item, so that lookup is never invoked.
• Full ./script/presubmit is not runnable on this machine (clang-format / wgslfmt / nextest gaps); the checks above are the runnable subset.

Smoke test (reviewer)

Run the 7b section of the Smoke test in roadmap/07-claude-code-panel/PRODUCT.md against a dogfood build (./script/run of the local warp bin, or --features claude_code_panel): toolbelt entry shows ("Claude Code"); ⌘⌥K toggles (opens+focuses when inactive, returns focus when active) and is rebindable; left-panel width persists across restart; zero state shows with no claude subprocess spawned; renaming/hiding claude on PATH shows the unavailable state.

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