Rename JSON mode → Chat, promote it as a first-class Claude interface - #82

… + tab header

Makes the Chat-vs-Terminal interface choice well-placed and discoverable
without changing the default (Terminal stays default for new installs).

Settings restructure:
- Removes the standalone `Experimental → JSON-mode Claude tabs`
  sub-card. The Interface picker (Terminal/Chat radio) now lives
  nested under the Default Agent → Claude row in Agent → General,
  rendered with the new `InterfaceToggle` component. The picker
  only shows when Claude is the selected default agent (Codex has
  no Chat-mode equivalent).
- Chat-specific config (default permission mode for new chats,
  auto-sleep idle minutes, chat density) moves to a `Chat interface`
  card under Agent → Claude — alongside the Claude command, env
  vars, etc.

`settings.jsonModeClaudeTabs` removed entirely (11 call sites,
under the spec's 10-site threshold but functionally a pure gate
that no longer has a "behind-a-flag" reason to exist). Default
behavior is now "Chat is always available; Terminal is still the
default." Persistence and IPC handler dropped along with the field;
existing configs with the key set are harmlessly ignored.

`defaultClaudeTabType` field stays unchanged — values continue to
be `'xterm' | 'json'` (no churn) but Settings now labels them
`Terminal` and `Chat`.

Onboarding:
- New `choose-interface` QuestStep, inserted between `hidden` and
  `spawn-second`. The QuestCard renders the same `InterfaceToggle`
  the Settings panel uses (size="compact"), with a Continue button
  that advances to `spawn-second`. Skip / dismiss defaults to
  Terminal (the existing `defaultClaudeTabType` default).

Per-tab switch chip:
- Every Claude tab header (agent.claude + json-claude) gets a small
  icon button (MessageSquare for Chat-bound switch, TerminalIcon
  for Terminal-bound) right before the close button, with a
  `Switch to Chat` / `Switch to Terminal` tooltip. Wires into the
  existing `convertTabType` IPC — no new plumbing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…erminal body

The per-tab icon chip felt cramped and easy to miss. The new affordance
overlays the Terminal Claude tab itself (top-left, mirroring the
top-right Spectating/Take-control overlay): a Sparkles icon plus
"Switch to the new Chat mode" — a discoverable nudge rather than a
generic toggle.

- TerminalPanel: drop the per-tab MessageSquare/TerminalIcon chip.
- XTerminal: new optional `onSwitchToChat` prop renders the chip
  when set, the tab is a Claude agent, and the terminal isn't
  loading/exited.
- WorkspaceView: thread `onSwitchToChat` through, wired to the
  existing `convertTabType('json-claude')` IPC for Claude agent
  tabs.

The reverse direction (Chat → Terminal) is still reachable via the
tab's right-click menu and the Settings interface picker. No need
to clutter the Chat body since Chat doesn't need promotion.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

There's no real cost meter UI in Chat — the description was forward-
looking and read oddly to users.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…hat tabs

The Terminal-tab Chat promo chip now ships with an X button that
persistently hides the nudge across the workspace. Once dismissed,
the user keeps Settings → Agent → Interface and right-click → Switch
to Chat as the discovery surfaces.

New `settings.chatPromotionDismissed: boolean` slice field (5-file
pattern: shared slice + test, persistence, initial-state, IPC,
backend method, type). Defaults to false.

On Chat tabs, when the user's default is still Terminal (i.e. they
transitioned from Terminal → Chat on this tab), a top-left overlay
shows two buttons:
- "Switch back" — calls `panesConvertTabType('agent')` to revert
  this tab to a Terminal Claude tab.
- "Set Chat as default" — calls `setDefaultClaudeTabType('json')`.
  Both overlay buttons auto-hide afterwards since the user is now
  at home in Chat.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

- "Switch back" → "Switch back to Terminal mode"
- "Set Chat as default" → "Make Chat mode default"
- Tooltips on the Switch-to-Chat, X dismiss, and Switch-back buttons
  point users at the right-click tab menu as a permanent alternative.
- Tooltip on the Make-Chat-default button points at Settings → Agent
  → Interface for reversing the choice later.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sends `app:debugResetOnboarding` from the Help menu (gated on
`!app.isPackaged`) and the renderer flips the quest back to
'hidden'. The choose-interface card resurfaces on the next worktree
tick. Lets us re-test the onboarding flow without nuking
`userData/config.json`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Big brand-gradient "What are we going to build today?" with a
Sparkles-in-a-gradient-circle above it, vertically centered in the
scroll area when the chat has no entries / pending approvals / busy
indicator. Subtitle "Send a message to get started." in muted
text. Hidden the moment the first entry lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Bare "Switch to Terminal" / "Switch to Chat" reads ambiguously (Terminal
what? Chat what?). Adding "mode" makes the right-click menu, the
sparkles button tooltip, and the Settings Interface radio match the
overlay copy already in place.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The empty-state hero (`min-h-full`) and the regular `px-4 py-3
space-y-3` content wrapper were both rendering when entries were
empty. The wrapper added ~24px of padding below the full-height
empty state, producing a tiny scrollable overflow. Switch to a
ternary so only one of the two trees mounts at a time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…in place

Repurposes the dev menu entry I added earlier. Instead of resetting
the QuestCard, it toggles a renderer-local override that forces the
4-step welcome / onboarding form to render even when repos are
already added, so the layout can be inspected without wiping
userData. A warning-tinted banner inside the form makes it obvious
we're in preview mode and offers an Exit preview button (toggling
the menu item again also exits).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The 4-step welcome form's "Choose your default agent" step now
reveals the Terminal/Chat InterfaceToggle right below the Claude
button when Claude is the selected default — same nested visual
pattern as Settings → Agent. Skipping it leaves the existing
'xterm' default in place.

Drops the post-creation QuestCard 'choose-interface' step now that
the welcome form covers it. QuestStep union goes back to the
original 5 values (hidden → spawn-second → switch-between → finale
→ done). QuestCard reverts to its pre-PR shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Subtle "Setting"-section flourish to draw the eye to the recently-
promoted Chat interface inside the Terminal/Chat radio. Uses the
same brand-gradient-bg as the Sparkles overlay button and onboarding
finale CTA for visual consistency.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>