Ship fake-engine dogfood and TUI default

[spytensor]

Closes #332
Updates #320

Summary

• Adds gated Engine::Fake behind COREROOM_ENABLE_FAKE_ENGINE=1, implemented through the existing EngineAdapter path with deterministic chunked output and a permission-bridge probe.
• Flips interactive plain cr to the executable full-screen TUI room from v0.9.x: implement TuiSink and ratatui room hosting run_with_options_and_sink #331. Non-TTY plain cr still falls back to the stdout runtime; cr start remains the explicit stdout entrypoint; cr console remains the read-only dashboard; cr console --live-room is the explicit TUI-room spelling.
• Rewrites the v0.9 dogfood harness to drive the TUI over a PTY, assert role status, streaming, permission overlay, and durable .coreroom/messages.jsonl events, then regenerates README images and updates v0.9.8 release docs/splash/version metadata.

Acceptance Criteria

• AC-1: Deterministic local fake engine implemented behind EngineAdapter; response text and chunk timing are env-configurable; no network/API path.
• AC-2: Fake engine is gated by COREROOM_ENABLE_FAKE_ENGINE=1; config validation and --engine fake reject it unless explicitly enabled.
• AC-3: scripts/dogfood-v09-user-cases.py drives the TUI room over PTY and checks idle/working status, streamed chunks, durable messages, and permission overlay behavior.
• AC-4: docs/v0.9-real-user-dogfood.md and docs/v0.9.4-live-room-dogfood.md now describe behavioral proof and authenticated-engine non-goals.
• AC-5: run_console_first_default routes interactive plain cr to the TUI room; cr start and cr console keep their existing roles.
• AC-6: README, CHANGELOG, splash content, v0.9.8 metadata, and README screenshot are updated; make readme-images ran via dogfood.
• AC-7: Validation and dogfood pass.
• AC-8: Dogfood proves execution through the fake engine plus default/explicit TUI routing. It does not prove authenticated Claude Code, Codex, or Gemini execution.

Validation

• cargo fmt --all -- --check passed.
• git diff --check passed.
• cargo clippy --all-targets --all-features --locked -- -D warnings passed.
• cargo test --all-features --locked passed: 608 lib tests passed, 1 ignored, integration/doc tests passed.
• python3 scripts/dogfood-v09-user-cases.py passed, including PTY plain cr, fake-engine streaming, permission overlay, durable messages.jsonl, cr console --live-room, read-only console paths, Nerd Font mode, and make readme-images.

Evidence Packet

The dogfood run proves executable-equivalent default behavior without quota burn:

• cr --version reported cr 0.9.8.
• Plain cr in a PTY rendered the TUI composer, dispatched fake-engine turns, showed idle and working, rendered fake-stream-1 through fake-stream-3, opened the FakeTool permission overlay, accepted denial, and rendered fake-permission-denied.
• .coreroom/messages.jsonl gained turn_dispatched, role_spoke, and permission_denied events with real turn ids.
• cr console --live-room opened the executable TUI room.
• cr console and cr console --snapshot remained read-only dashboard paths.
• make readme-images regenerated docs/images/boot-dashboard.png, docs/images/work-cards.png, and docs/images/control-room-console.png; only boot-dashboard.png changed with v0.9.8 splash copy.

Changed Files Summary

• Runtime/config: src/adapter/fake.rs, src/adapter/mod.rs, src/repl.rs, src/main.rs, src/config*.rs, src/engines.rs, init/splash labels.
• Dogfood/docs: scripts/dogfood-v09-user-cases.py, v0.9 dogfood docs, README, CHANGELOG, development notes, proposed amendment note.
• Release metadata/assets: Cargo/npm versions to 0.9.8, src/lib.rs docs root, splash content, README image.

Risks and Remaining Gaps

• Fake-engine dogfood proves CoreRoom runtime/TUI/permission/durable-event plumbing, not real vendor CLI authentication or model behavior.
• The fake engine is intentionally hidden from normal engine help and rejected unless the env gate is set.
• macOS Unix socket path length is covered by the dogfood harness using a short /tmp/cr-v09-* project path.

Rollback Plan

Revert this PR to restore plain cr to the previous default path, remove the fake engine adapter, and restore the previous v0.9.7 docs/assets. If only the TUI default is problematic, revert the run_console_first_default change and leave cr console --live-room as the explicit executable TUI entrypoint.

Tracker Update

After merge, update #320:

• Check AC-6: deterministic fake-engine PTY dogfood now proves runtime dispatch, streaming, permission prompt, completion, and durable transcript state.
• Check AC-7: plain cr now defaults to the executable full-screen TUI room.
• Progress ledger: add this PR with validation evidence above and note remaining risk is authenticated vendor-engine dogfood only.
• Close v0.9.x: implement true full-screen runtime parity before making live room default #320 once the tracker body reflects AC-1 through AC-7 complete.