docs: archive shipped openspec batches; add feature/plan/research notes

Move 13 shipped openspec change docs under openspec/changes/archived/.
Add docs/features/git-diff-panel, docs/plans/post-review-backlog, and
docs/research/cross-app-contract-ssot.md (the research behind the
@boocode/contracts SSOT work). Update BOOCHAT.md, BOOCODER.md, and
boocode_roadmap.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

BOOCHAT.md

@@ -28,6 +28,11 @@
 - Prefer codecontext (`search_symbols`, `get_symbol_info`, `get_dependencies`) over `grep` for symbol-level questions. Fall back to `grep` / `view_file` when codecontext returns degraded or empty results — that signals an unsupported language or parse failure.
 - Verify before reporting work complete: run the relevant test/build/smoke command and confirm output matches the claim. Evidence first, assertion second.
 
+## Recovery and context (v2.7)
+
+- **Heed the recovery nudge.** Native inference tracks consecutive tool **failures** (`mistake-tracker.ts`): after 3 in a row with no successful step between, a `mistake_recovery` sentinel is injected telling you to re-read tool schemas, verify a path exists before acting, and try a *different* approach — not retry variations of the same failing call. Ignoring it (a second failure run with the nudge still outstanding) **escalates and stops the turn** to protect the step budget. This complements the doom-loop guard, which only catches *identical* repeats.
+- **Files-read provenance survives compaction.** Paths you read via `view_file` / `grep` / `find_files` / `list_dir` are accumulated and merged into a cumulative `## Files Read` ledger in the rolling summary, so a file read long ago stays in context across compactions. You don't manage this — but it means you usually don't need to re-read a file just because the raw turn scrolled out of the window.
+
 ## Output format
 
 - Stay in Markdown by default for every reply, short or long.