refactor: remove turn tools, rename discord tools, rewrite installer

- Remove turn management tools (turn-status/advance/reset) — internal only,
  accessible via /dirigent slash commands
- Rename discord tools: dirigent_discord_channel_create,
  dirigent_discord_channel_update, dirigent_discord_member_list
- Rewrite install script:
  - Dynamic OpenClaw dir resolution (OPENCLAW_DIR env → openclaw CLI → ~/.openclaw)
  - Plugin installed to $(openclaw_dir)/plugins/dirigent
  - New --update mode: git pull from latest branch + reinstall
  - Cleaner uninstall: removes installed plugin files
- Update docs (FEAT.md, README.md, CHANGELOG.md, TASKLIST.md)

README.md

@@ -78,22 +78,19 @@ Discord extension capabilities: `docs/DISCORD_CONTROL.md`.
 
 ## Runtime tools & commands
 
-### Tools (9 individual tools)
+### Tools (6 individual tools)
 
 **Discord control:**
-- `dirigent_channel_create` — Create private channel
-- `dirigent_channel_update` — Update channel permissions
-- `dirigent_member_list` — List guild members
+- `dirigent_discord_channel_create` — Create private channel
+- `dirigent_discord_channel_update` — Update channel permissions
+- `dirigent_discord_member_list` — List guild members
 
 **Policy management:**
 - `dirigent_policy_get` — Get all policies
 - `dirigent_policy_set` — Set/update channel policy
 - `dirigent_policy_delete` — Delete channel policy
 
-**Turn management:**
-- `dirigent_turn_status` — Show turn state
-- `dirigent_turn_advance` — Advance turn
-- `dirigent_turn_reset` — Reset turn order
+> Turn management is internal to the plugin (not exposed as tools).
 
 > See `FEAT.md` for full feature documentation.