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>

AGENTS.md

@@ -73,6 +73,7 @@ If any required file is missing, you MUST stop and report the missing file.
 34. For source-code delivery through PR workflow, completion is forbidden until the PR is merged to `main`, CI/pipeline status is terminal green, and linked issue/internal task is closed.
 35. If merge/CI/issue-closure operations fail, you MUST report a blocker with the exact failed wrapper command and stop instead of declaring completion.
 36. Before push or PR merge, you MUST run CI queue guard and wait if the project has running/queued pipelines: `~/.config/mosaic/tools/git/ci-queue-wait.sh --purpose push|merge`.
+37. When an active mission is detected at session start (MISSION-MANIFEST.md, TASKS.md, or scratchpads/ present), you MUST load `~/.config/mosaic/guides/ORCHESTRATOR-PROTOCOL.md` and follow the Session Resume Protocol before taking any action.
 
 ## Mode Declaration Protocol (Hard Rule)
 
@@ -112,6 +113,7 @@ Load additional guides when the task requires them.
 | QA and test strategy | `~/.config/mosaic/guides/QA-TESTING.md` |
 | Secrets and vault usage | `~/.config/mosaic/guides/VAULT-SECRETS.md` |
 | Orchestrator estimation heuristics | `~/.config/mosaic/guides/ORCHESTRATOR-LEARNINGS.md` |
+| Mission lifecycle / multi-session orchestration | `~/.config/mosaic/guides/ORCHESTRATOR-PROTOCOL.md` |
 
 ## Embedded Delivery Cycle (Hard Rule)