feat: r0 coordinator tooling for orchestrator protocol

Implements the manual coordinator workflow for multi-session agent
orchestration. Agents stop after one milestone (confirmed limitation);
these tools let the human coordinator check status, generate continuation
prompts, and chain sessions together.

New:
- tools/orchestrator/ — 5 scripts + shared library (_lib.sh)
  - mission-init.sh: initialize mission with milestones and state files
  - mission-status.sh: dashboard showing milestones, tasks, sessions
  - session-status.sh: check if agent is running/stale/dead
  - continue-prompt.sh: generate paste-ready continuation prompt
  - session-resume.sh: crash recovery with dirty state detection
- guides/ORCHESTRATOR-PROTOCOL.md: agent-facing mission lifecycle guide
- templates/docs/: mission manifest, scratchpad, continuation templates
- templates/repo/.mosaic/orchestrator/mission.json: state file template

Modified:
- bin/mosaic: add 'coord' subcommand + resume advisory on launch
- AGENTS.md: conditional loading for protocol guide + rule 37
- bin/mosaic-doctor: checks for new coordinator files
- session hooks: mission detection on start, cleanup on end

Usage: mosaic coord init|mission|status|continue|resume

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/docs/MISSION-MANIFEST.md.template

@@ -0,0 +1,53 @@
+# Mission Manifest — ${MISSION_NAME}
+
+> Persistent document tracking full mission scope, status, and session history.
+> Updated by the orchestrator at each phase transition and milestone completion.
+
+## Mission
+
+**ID:** ${MISSION_ID}
+**Statement:** ${MISSION_STATEMENT}
+**Phase:** Intake
+**Current Milestone:** —
+**Progress:** 0 / ${MILESTONE_COUNT} milestones
+**Status:** not-started
+**Last Updated:** ${CREATED_AT}
+
+## Success Criteria
+
+${SUCCESS_CRITERIA}
+
+## Milestones
+
+| # | ID | Name | Status | Branch | Issue | Started | Completed |
+|---|-----|------|--------|--------|-------|---------|-----------|
+${MILESTONES_TABLE}
+
+## Deployment
+
+| Target | URL | Method |
+|--------|-----|--------|
+${DEPLOYMENT_TABLE}
+
+## Coordination
+
+- **Primary Agent:** ${PRIMARY_RUNTIME}
+- **Sibling Agents:** ${SIBLING_AGENTS}
+- **Shared Contracts:** ${SHARED_CONTRACTS}
+
+## Token Budget
+
+| Metric | Value |
+|--------|-------|
+| Budget | ${TOKEN_BUDGET} |
+| Used | 0 |
+| Mode | normal |
+
+## Session History
+
+| Session | Runtime | Started | Duration | Ended Reason | Last Task |
+|---------|---------|---------|----------|--------------|-----------|
+
+## Scratchpad
+
+Path: `docs/scratchpads/${MISSION_ID}.md`