TUI: replace the wizard-replay ⌥s with a proper settings card

[codyde]

What

⌥s used to replay the entire first-run wizard, and ⌥t cycled the theme blind — two chords on the main screen, one of them a four-step flow, to change a single answer.

⌥s now opens a settings card listing every preference from agent-prefs.json with its current value beside it:

╭─ settings ───────────────────────────────────────╮
│               Cloud agent settings               │
│                                                  │
│ ▌ Coding agent        ‹ claude ›                 │
│      Anthropic's Claude Code                     │
│   Default project     devtools (production)      │
│      Where new cloud agents are created          │
│   Skills sync         on · claude                │
│      Copied to the agent at launch               │
│   Theme               Railway                    │
│      Previews as you cycle                       │
│   Run first-time setup again                     │
│                                                  │
│   ↑↓ choose  ←→ change  enter edit  esc close    │
╰──────────────────────────────────────────────────╯

• Agent, skills, theme cycle in place with ←/→ (enter also steps forward). The theme repaints the whole screen as it cycles, like the wizard's theme step.
• Every change saves immediately, merged over the prefs file on disk so the skills exclude list survives; esc is only ever "close" — no dirty state, no confirm.
• Default project opens a sub-picker (the wizard's project question: existing projects, "create a project" incl. the async create + spinner/error handling, "decide later" to clear the default) and returns straight to the card.
• A last row replays first-run setup for anyone who wants the guided walk. The wizard itself is unchanged and remains the first-run flow.

Retired

• ⌥t is gone — the theme now lives (and persists, which ⌥t never did) on the settings card. Its composed form † falls through as plain text like any unclaimed Option-character.
• Footer chords read ⌥s settings instead of ⌥t theme · ⌥s setup.

Implementation

• New tui/settings.rs model mirroring wizard.rs's shape (Action enum, busy/error, narrative tests); reuses wizard::Outcome/ProjectOption and newly-extracted project_options()/harness_blurb().
• New Screen::Settings + Effect::SaveSettings, handled in the event loop next to SaveSetup; Message::ProjectCreated now routes to whichever of wizard/settings is open.
• Rendering reuses render_panel; the one shared tweak is that a row's dim tag brightens while its row is selected.
• App gains skills_enabled, mirrored from prefs at startup so the card opens showing the saved answer.

Testing

• cargo test cloud_agent: 256 passed (includes new settings model, key-routing, and draw tests).
• cargo fmt --check, cargo clippy: clean in touched files.
• Full suite: the only failures are the 3 pre-existing auth_sim tests, which also fail on a clean origin/master checkout in this environment (they pick up the machine's real Railway credentials).

Also: ⌥esc replaces shift+esc

Standardizing the TUI's own chords on one modifier family (⌥f, ⌥], ⌥s, ⌥esc): releasing a focused session is now ⌥esc / ^] instead of shift+esc / ^]. The trade is symmetric — both spellings require the enhanced keyboard protocol to be reportable at all (a plain terminal folds either into a bare Escape meant for the agent, and crossterm parses classic ESC ESC as plain Esc), so ^] and ^o remain the universal fallbacks. One platform note: Alt+Esc is an OS shortcut on Windows, where ^] is the way out.

Also: ⌥enter replaces shift+enter for full screen

shift+enter is the newline every text field gives you, and the harnesses running in a session bind it that way — so the TUI shouldn't reserve it. "Leave the TUI and connect full screen" moves to ⌥enter, joining the same ⌥ family; f stays as the fallback for terminals that send no modifier with Enter.

⌥enter is actually more reportable than the chord it replaces: a terminal with Option-as-Meta sends ESC CR, which crossterm parses as Alt+Enter with no enhanced keyboard protocol needed, whereas shift+enter strictly required it.

Note this binding only ever fired with the tree focused — a focused session already forwards everything except ⌥f/⌥]/the release chords — so this is about which key the TUI reserves, not about what the pane passes through. A test now pins shift+enter as unclaimed from either focus.

Follow-up worth a separate PR

Freeing the binding is necessary but not sufficient for shift+enter to insert a newline in an embedded pane. session::encode_key currently discards the shift modifier (let _ = shift;) and encodes Enter as a bare \r regardless, so a harness inside the pane sees shift+enter and plain enter as the same byte and submits. Making it a newline means encoding it distinguishably — either kitty CSI-u (\x1b[13;2u, only understood if the harness negotiated that protocol, and literal garbage if it didn't) or translating it to ESC CR, the alt+enter newline chord harnesses already accept. That's a change to what bytes reach the agent, so it isn't bundled here. Full-screen sessions are unaffected either way — they bypass the emulator entirely.