v0.8: Implement CREP to ConsoleState reducer and conversation viewport

[spytensor]

Context

The future console needs a replayable state layer. Today REPL rendering is largely event-to-string/println. v0.8 needs a pure reducer that can replay CREP events into console state and conversation viewport models.

Acceptance Criteria

• AC-1: Add a reducer that applies CREP events into console/conversation state without printing.
• AC-2: Cover role started, turn dispatched, role spoke/output, tool events, permission denied/approved, phase advanced/blocked, and handoff-like events where supported.
• AC-3: Replaying a fixture log yields deterministic conversation viewport output.
• AC-4: Public transcript filtering respects the visibility model from the relevant v0.8 issue.
• AC-5: Stream deltas can be folded or summarized for viewport rendering.
• AC-6: Tests cover malformed/partial event replay behavior without treating skipped malformed lines as evidence.

Evidence Required

• Reducer module.
• CREP fixture.
• Unit/replay tests.
• Validation commands.
• Risk and rollback.

Tracker Update Required

This issue is incomplete until tracker #238 is updated.

• Tick this issue checkbox in v0.8.0 - CoreRoom Console Data Plane Tracker #238.
• Update any satisfied milestone AC in v0.8.0 - CoreRoom Console Data Plane Tracker #238.
• Update the Evidence Ledger row in v0.8.0 - CoreRoom Console Data Plane Tracker #238.
• Mention the tracker update in PR body.

If implementation is complete but tracker is stale, report implementation complete, tracker incomplete.

Out Of Scope

• No ratatui renderer.
• No change to CREP wire format unless strictly required and documented.
• No mutation actions from reducer output.