refactor(claude-md): split shared base into module fragments, inject name at runtime

Move every agent-specific instruction out of the shared container/CLAUDE.md
so the base is genuinely universal. Persona/identity now comes from the
system-prompt addendum (buildSystemPromptAddendum now takes assistantName
and prepends "# You are {name}"). Per-module instructions live alongside
each MCP tool source:

  container/agent-runner/src/mcp-tools/core.instructions.md
  container/agent-runner/src/mcp-tools/scheduling.instructions.md
  container/agent-runner/src/mcp-tools/self-mod.instructions.md

composeGroupClaudeMd() scans that directory and emits `module-<name>.md`
fragments as symlinks to /app/src/mcp-tools/<name>.instructions.md (valid
via the existing RO source mount). Skill fragments renamed to
`skill-<name>.md` for naming consistency with `module-*` and `mcp-*`.

Mount tightening so composer-managed files can't be clobbered by agent
writes: nested RO mounts for /workspace/agent/CLAUDE.md and
/workspace/agent/.claude-fragments/. CLAUDE.local.md (per-group memory)
stays RW as the only writable CLAUDE.md-family file.

.gitignore: ignore CLAUDE.local.md, .claude-shared.md, .claude-fragments/
everywhere, and simplify groups/ rules to ignore the whole tree (per-
installation state, not tracked).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

container/agent-runner/src/mcp-tools/scheduling.instructions.md

@@ -0,0 +1,40 @@
+## Task scheduling (`schedule_task`)
+
+For any recurring task, use `schedule_task`. This is the scheduling path — tasks persist across sessions and restarts, and support the pre-task `script` hook described below.
+
+To inspect or change existing tasks, use `list_tasks` (returns one row per series with the stable id) and `update_task` / `cancel_task` / `pause_task` / `resume_task`. Prefer `update_task` over cancel + reschedule.
+
+Frequent recurring scheduled tasks — more than a few times a day — consume API credits and can risk account restrictions. You can add a `script` that runs first, and you will only be called when the check passes.
+
+### How it works
+
+1. Provide a bash `script` alongside the `prompt` when scheduling
+2. When the task fires, the script runs first
+3. Script returns: `{ "wakeAgent": true/false, "data": {...} }`
+4. If `wakeAgent: false` — nothing happens, task waits for next run
+5. If `wakeAgent: true` — claude receives the script's data + prompt and handles
+
+### Always test your script first
+
+Before scheduling, run the script directly to verify it works:
+
+```bash
+bash -c 'node --input-type=module -e "
+  const r = await fetch(\"https://api.github.com/repos/owner/repo/pulls?state=open\");
+  const prs = await r.json();
+  console.log(JSON.stringify({ wakeAgent: prs.length > 0, data: prs.slice(0, 5) }));
+"'
+```
+
+### When NOT to use scripts
+
+If a task requires your judgment every time (daily briefings, reminders, reports), skip the script — just use a regular prompt. Do not attempt to do things like sentiment analysis or advanced nlp in scripts.
+
+### Frequent task guidance
+
+If a user wants a task to run more than a few times a day and a script can't be used:
+
+- Explain that each time the task fires it uses API credits and risks rate limits
+- Suggest adjusting the task requirements in a way that will allow you to use a script
+- If the user needs an LLM to evaluate data, suggest using an API key with direct Anthropic API calls inside the script
+- Help the user find the minimum viable frequency