Add conversation, workspace, and evidence drill-down views #8

Context

PR #2 establishes progressive disclosure with a custody spine and compact activity list. It intentionally omits transcript, diff, validation-detail, proof-artifact, and handoff views so the first projection contract stays reviewable.

Scope

Add detail modes for:

• transcript/conversation projection without raw-log dominance;
• touched files, worktree identity, and compact diff summaries;
• validation gate details and failure causes;
• proof references/artifacts and evidence provenance;
• handoff summary, decision, and next-owner context.

Preserve the calm default: the selected intent and human attention state must remain primary, while verbose event streams and raw source payloads stay opt-in.

Non-goals

No full chat product, editor, patch application, raw stdout wall, invented progress metrics, or independent persistence of governance/evidence state.

Acceptance criteria

• Each drill-down is reachable from the current keyboard model without losing the selected intent.
• Every detail displays source type, source timestamp/freshness, and custody correlation where available.
• Missing or unavailable evidence is labeled as unknown/unavailable rather than blank or successful.
• Validation failures and proof failures remain inspectable in Quiet mode through attention/status and in detail through causes/references.
• Narrow terminals degrade predictably and do not panic.
• Semantic UI tests cover active, blocked, failed, stale, unavailable, conflicted, ready, and handed-off states.

Dependencies

PR #2 projection and UI foundation; authoritative Decapod enrichment; real Pincher adapter.

Validation expectations

Run semantic view-model tests, TestBackend rendering tests at narrow widths, cargo fmt/test/Clippy, and Decapod validation.

Related: #2