fix: resolve telegram/slack name collision between tool and channel registries (#346)

When installing the Telegram WASM channel via the web UI, a name collision
between registry/tools/telegram.json and registry/channels/telegram.json
caused the tool entry to win, installing to ~/.ironclaw/tools/ instead of
~/.ironclaw/channels/. This made activation fail with "WASM runtime not
available".

- Add `get_with_kind()` to ExtensionRegistry for kind-aware lookup
- Use `kind_hint` parameter in `install()` to resolve collisions
- Rename tool entries to avoid future collisions: telegram → telegram-mtproto,
  slack → slack-tool
- Fix `_bundles.json` stale reference (tools/slack → tools/slack-tool)
- Fix `cache_discovered()` to deduplicate by (name, kind) consistently
- Add path traversal validation to install/activate/remove entry points
- Add tests for kind-aware lookup, discovery cache, and bundle resolution

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

registry/tools/slack.json

@@ -1,5 +1,5 @@
 {
-  "name": "slack",
+  "name": "slack-tool",
   "display_name": "Slack",
   "kind": "tool",
   "version": "0.1.0",