feat(tools): add session management tools for OpenCode sessions (#227)

* feat(tools): add session management tools for OpenCode sessions

- Add session_list tool for listing sessions with filtering
- Add session_read tool for reading session messages and history
- Add session_search tool for full-text search across sessions
- Add session_info tool for session metadata inspection
- Add comprehensive tests for storage, utils, and tools
- Update documentation in AGENTS.md

Closes #132

* fix(session-manager): add Windows compatibility for storage paths

- Create shared/data-path.ts utility for cross-platform data directory resolution
- On Windows: uses %LOCALAPPDATA% (e.g., C:\Users\Username\AppData\Local)
- On Unix: uses $XDG_DATA_HOME or ~/.local/share (XDG Base Directory spec)
- Update session-manager/constants.ts to use getOpenCodeStorageDir()
- Update hook-message-injector/constants.ts to use same utility
- Remove dependency on xdg-basedir package in session-manager
- Follows existing pattern from auto-update-checker for consistency

---------

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/tools/index.ts

@@ -21,6 +21,13 @@ import { grep } from "./grep"
 import { glob } from "./glob"
 import { slashcommand } from "./slashcommand"
 
+import {
+  session_list,
+  session_read,
+  session_search,
+  session_info,
+} from "./session-manager"
+
 export { interactive_bash, startBackgroundCheck as startTmuxCheck } from "./interactive-bash"
 export { getTmuxPath } from "./interactive-bash/utils"
 
@@ -63,4 +70,8 @@ export const builtinTools = {
   grep,
   glob,
   slashcommand,
+  session_list,
+  session_read,
+  session_search,
+  session_info,
 }