Add tmux pane management for background agent sessions (#1094)

* feat(config): add TmuxConfigSchema for tmux subagent pane management

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* feat(shared): add tmux module structure

* feat(shared/tmux): implement tmux pane utilities

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* test(tmux-subagent): add TmuxSessionManager tests (TDD RED)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* feat(tmux-subagent): implement TmuxSessionManager

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* feat(integration): wire TmuxSessionManager with 500ms delay

- Task 5: Add 500ms delay in BackgroundManager after session creation
- Task 6: Wire TmuxSessionManager event handlers (session.created/deleted)
- Both changes integrate tmux pane management into plugin lifecycle

Co-authored-by: Sisyphus <ultrawork@oh-my-opencode>

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Co-authored-by: Sisyphus <ultrawork@oh-my-opencode>

src/shared/tmux/constants.ts

@@ -0,0 +1,11 @@
+// Polling interval for background session status checks
+export const POLL_INTERVAL_BACKGROUND_MS = 2000
+
+// Maximum idle time before session considered stale
+export const SESSION_TIMEOUT_MS = 10 * 60 * 1000  // 10 minutes
+
+// Grace period for missing session before cleanup
+export const SESSION_MISSING_GRACE_MS = 6000  // 6 seconds
+
+// Delay after pane spawn before sending prompt
+export const PANE_SPAWN_DELAY_MS = 500