Cancel individual bot rounds while keeping issue tracking

[d3cker]

Stopping an unwanted feedback round currently ends tracking for the whole issue, even when its PR remains open. Add separate /bot actions and CLI/RPC commands to cancel only the current round or explicitly resume tracking a locally closed issue.

• Cancel current round checkpoints cancelling, interrupts saved sessions, drains in-flight local work and question posts, then archives the round and enters watching. It never publishes that round automatically. New queued feedback remains eligible; interruption failures and service restarts resume the durable cancellation.
• Resume issue tracking validates the open issue and known PR, skips the abandoned round and observed closed-period backlog, and watches future comments without immediately replaying work.
• The next round uses a fresh local branch/worktree from the remote PR head or pinned base. Cancelled worktrees, dirty files and local commits remain intact; publication still targets the original PR branch. Normal later rounds reuse the new worktree.
• While watching, merge approval checks use only the last saved published head. Legacy checkpoints lacking that head continue watching comments and PR state but cannot auto-merge until another successful publication. Publication/merge already in flight rejects cancellation rather than claiming to undo remote effects.
• Closed/watching tasks no longer show old session errors or failed-attempt counters as current failures. Details retain historical errors and the preserved worktree. Operator control versions prevent stale UI events from reviving cancelled or previously closed work.

Documentation includes README, architecture, runtime commands, recovery/persistence, migration limits, all eight affected workflow diagrams, AGENTS, bundled bot instructions and Unreleased notes. Old plugin versions cannot read the new statuses after use; retain a coordinated backup for rollback.

Validation: npm run check passed (209 tests, lint, typecheck, native TUI rendering and build). Real Git coverage verifies that both dirty files and unpublished commits stay in the cancelled worktree while the next round updates the existing remote branch. Tests also cover late checkpoints, cancellation during verification, publication exclusion, restart/interruption failures, failed final state writes, closed-task resumption, permission-reply suppression, safe merge heads and stale UI events. The final package passed an isolated installation check. All eight Mermaid diagrams parse, 90 local documentation links pass, and git diff --check passes.

Targets devel; no release, version bump, live task resumption or server deployment is included.