v0.9.7: restore truthful default execution path

[spytensor]

Context

v0.9.5 made plain cr enter the unified live room by default, but the live room bridge is still a staged renderer/router. It records user input in an in-memory snapshot and marks a role lane as working, but it does not spawn role engines, does not stream model output, does not surface the mature permission prompt socket, and does not persist the submitted turn as a real REPL turn.

That makes the default product path truthfully worse than the legacy executable path: after the user submits input, the room can show @host working / received the request while no role is actually doing the work.

Acceptance Criteria

• AC-1: Plain cr no longer defaults to the staged live-room bridge for initialized interactive projects.
• AC-2: Plain cr reaches the mature executable runtime path that spawns configured roles, preserves session resume behavior, streams work status, and uses the existing permission prompt path.
• AC-3: cr start remains accepted as the explicit direct runtime entrypoint.
• AC-4: cr console remains the read-only dashboard/snapshot inspection surface.
• AC-5: cr console --live-room remains available only as an explicit preview/staging surface until runtime parity is implemented.
• AC-6: README, CHANGELOG, and v0.9 dogfood docs explain that v0.9.7 restores the executable default path and does not claim full-screen runtime parity.
• AC-7: Validation proves the default path no longer renders CoreRoom Workspace / Ask @host before execution; the live-room alias remains separately testable.

Required Evidence

• Code diff showing the default entrypoint routes to the executable runtime instead of run_live_room_console.
• PTY or unit evidence that plain cr no longer opens the staged live room by default.
• Updated v0.9 dogfood docs and release notes.
• Validation commands: cargo fmt --all -- --check, targeted cargo tests, git diff --check.

Non-goals

• Full ratatui runtime parity.
• Removing the live-room preview alias.
• Replacing the existing REPL runtime.

Tracker Update Required

This hotfix is incomplete until the PR evidence lists satisfied ACs, remaining runtime-parity gaps, and the v0.9 tracker/evidence ledger state.