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

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+# 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`

templates/docs/continuation-prompt.md.template

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+## Continuation Mission
+
+Continue **${MISSION_NAME}** from existing state.
+
+## Setup
+
+- **Project:** ${PROJECT_PATH}
+- **State:** docs/TASKS.md (already populated — ${TASKS_DONE}/${TASKS_TOTAL} tasks complete)
+- **Manifest:** docs/MISSION-MANIFEST.md
+- **Scratchpad:** docs/scratchpads/${MISSION_ID}.md
+- **Protocol:** ~/.config/mosaic/guides/ORCHESTRATOR.md
+- **Quality gates:** ${QUALITY_GATES}
+
+## Resume Point
+
+- **Current milestone:** ${CURRENT_MILESTONE_NAME} (${CURRENT_MILESTONE_ID})
+- **Next task:** ${NEXT_TASK_ID}
+- **Progress:** ${TASKS_DONE}/${TASKS_TOTAL} tasks (${PROGRESS_PCT}%)
+- **Branch:** ${CURRENT_BRANCH}
+
+## Previous Session Context
+
+- **Session:** ${PREV_SESSION_ID} (${PREV_RUNTIME}, ${PREV_DURATION})
+- **Ended:** ${PREV_ENDED_REASON}
+- **Last completed task:** ${PREV_LAST_TASK}
+
+## Instructions
+
+1. Read `~/.config/mosaic/guides/ORCHESTRATOR.md` for full protocol
+2. Read `docs/MISSION-MANIFEST.md` for mission scope and status
+3. Read `docs/scratchpads/${MISSION_ID}.md` for session history and decisions
+4. Read `docs/TASKS.md` for current task state
+5. `git pull --rebase` to sync latest changes
+6. Continue execution from task **${NEXT_TASK_ID}**
+7. Follow Two-Phase Completion Protocol
+8. You are the SOLE writer of `docs/TASKS.md`

templates/docs/mission-scratchpad.md.template

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+# Mission Scratchpad — ${MISSION_NAME}
+
+> Append-only log. NEVER delete entries. NEVER overwrite sections.
+> This is the orchestrator's working memory across sessions.
+
+## Original Mission Prompt
+
+```
+${MISSION_PROMPT}
+```
+
+## Planning Decisions
+
+<!-- Record key decisions made during planning. Format: decision + rationale. -->
+
+## Session Log
+
+| Session | Date | Milestone | Tasks Done | Outcome |
+|---------|------|-----------|------------|---------|
+
+## Open Questions
+
+<!-- Unresolved items that need human input or cross-session investigation. -->
+
+## Corrections
+
+<!-- Record any corrections to earlier decisions or assumptions. -->