feat(opencode): one-task-per-run model + 9 routing fixes (ADRs 13-21)
Captures the design grilling outcome. Adds ADRs 13-21 covering:
- run-level plan_rework_remaining counter to bound P3<->P5.5/P7/P8 thrash
- non-resumable workflow with throwaway-worktree recovery procedure
- @simplify advisory at every gate (not just Phase 8)
- Phase 8 fix specs go to disk as task-fix-N.md (preserves ADR-6)
- Phase 5.5 BLOCK protocol: orchestrator edits plan, decrements counter, re-enters P4
- Phase 8 NOT_TESTABLE manifest in reviewer prompt
- unified Implementation Incomplete diagnosis (test_design / production_logic / split_needed)
- Phase 1 working-tree cleanliness + depends-on enforcement
- one-task-per-run pivot: Phase 5 still splits N tasks, only task-1 runs;
tasks 2..N filed as sub-issues with rich seed bodies; split_needed at P7
aborts to Failure Handler (one-task-per-run = no salvageable prior work)
Auto-resolves big-diff Phase 8 reviews, cross-task regression-within-run, and
mid-flight task-split routing. Rewrites routing matrix and three Mermaid
diagrams; updates @pm (depends-on frontmatter, split-time filing), @check
(third diagnosis verdict), @make (escalate: split_needed flag).