chore: add project meta files and Claude behavioral guide

Add TODO.md, CHANGELOG.md, .claude/CLAUDE.md behavioral guide.
Update README.md with v2 planning notice and docs links.
Fix .gitignore to scope CLAUDE.md exclusion to root only.

.claude/CLAUDE.md

@@ -0,0 +1,34 @@
+# BTerminal — Claude Behavioral Guide
+
+## Workflow
+
+- v1 is a single-file Python app (`bterminal.py`). Changes are localized.
+- v2 planning docs are in `docs/`. Architecture decisions are in `docs/task_plan.md`.
+- Consult Memora (tag: `bterminal`) before making architectural changes.
+
+## Documentation References
+
+- Architecture & decisions: [docs/task_plan.md](../docs/task_plan.md)
+- Implementation phases: [docs/phases.md](../docs/phases.md)
+- Research findings: [docs/findings.md](../docs/findings.md)
+- Progress log: [docs/progress.md](../docs/progress.md)
+
+## Rules
+
+- Do not modify v1 code (`bterminal.py`) unless explicitly asked — it is production-stable.
+- v2 work goes on a feature branch (`v2-mission-control`), not master.
+- All v2 architecture decisions must reference `docs/task_plan.md` Decisions Log.
+- When adding new decisions, append to the Decisions Log table with date.
+- Update `docs/progress.md` after each significant work session.
+
+## Key Technical Constraints
+
+- WebKit2GTK has no WebGL — xterm.js must use Canvas addon explicitly.
+- Claude Agent SDK is 0.2.x (pre-1.0) — all SDK interactions go through the adapter layer (`src/lib/adapters/sdk-messages.ts`).
+- Node.js sidecar communicates via stdio NDJSON, not sockets.
+- Maximum 4 active xterm.js instances to avoid WebKit2GTK memory issues.
+
+## Memora Tags
+
+Project tag: `bterminal`
+Common tag combinations: `bterminal,architecture`, `bterminal,research`, `bterminal,tech-stack`