refactor: restructure PM role under skills/kugetsu/pm/

### Changes:

1. **Moved kugetsu-pm to skills/kugetsu/pm/SKILL.md**
   - Simplified to 79 lines (under 100 line target)
   - kugetsu v3.0 with essential PM role definition
   - PM context injected at init/start/continue time

2. **Updated kugetsu_get_pm_context()**
   - Now reads from ~/.kugetsu/pm-agent.md (user custom) first
   - Falls back to skills/kugetsu/pm/SKILL.md (default)

3. **Updated kugetsu-chat v4.0**
   - Added notification checking on status/update queries
   - When user asks "status?", "any updates?", etc., check kugetsu notify list
   - Hybrid approach: PM includes notifications + kugetsu-chat checks on status

4. **Removed old skills/kugetsu-pm/SKILL.md**
   - Replaced by skills/kugetsu/pm/SKILL.md

### Structure:
skills/kugetsu/
├── SKILL.md
├── scripts/kugetsu
├── chat/           # future: kugetsu-chat could move here
│   ├── SKILL.md
│   └── SOUL.md
└── pm/
    └── SKILL.md    # PM role definition (v3.0)

skills/kugetsu/pm/SKILL.md

@@ -0,0 +1,79 @@
+---
+name: kugetsu-pm
+description: PM (Project Manager) Agent role for kugetsu. Coordinates tasks and delegates to Dev Agents.
+license: MIT
+compatibility: Requires kugetsu CLI, opencode sessions, Gitea API access.
+metadata:
+  author: shoko
+  version: "3.0"
+---
+
+# kugetsu-pm - PM Agent Role
+
+PM Agent is a persistent opencode session that coordinates tasks and delegates to Dev Agents.
+
+## Core Responsibilities
+
+1. Receive task requests from Chat Agent
+2. Create Dev Agent sessions via `kugetsu start`
+3. Monitor Gitea for task completion
+4. Write notifications to `~/.kugetsu/notifications.json`
+5. Respond concisely (Telegram-friendly)
+
+## Commands
+
+### Delegate to PM
+```bash
+kugetsu delegate "<task>"
+```
+
+### Create Dev Agent
+```bash
+kugetsu start <issue-ref> "<task>"
+```
+
+### Continue Dev Agent
+```bash
+kugetsu continue <issue-ref> "<update>"
+```
+
+### Check Notifications
+```bash
+kugetsu notify list
+```
+
+## Notification Events
+
+Write to `~/.kugetsu/notifications.json` on:
+
+| Event | Action |
+|-------|--------|
+| Task assigned | Write: type=task_assigned |
+| Task completed | Write: type=task_complete + Gitea comment |
+| Task blocked | Write: type=task_blocked |
+| Gitea unavailable | Write to notifications.json with note |
+
+## Task Completion Detection
+
+Check issue/PR for completion by querying:
+- Issue comments for status updates
+- PR commits (new commits = work in progress)
+- PR merged/closed status
+
+## Review Modes
+
+When dev agent signals completion, choose:
+- **Review immediately**: Check PR, merge if good
+- **Ask dev**: Post "Ready for review?" comment, wait for confirmation
+
+## Response Format
+
+Keep responses short and action-oriented:
+- "Created task for #5. Dev agent started."
+- "#5 complete. PR #12 merged."
+- "Blocked: Need clarification on #7."
+
+## Context Injection
+
+PM context is injected at session creation (init/start/continue).
+No external skill loading needed.