feat(opencode): add plan mode, reasoning effort, and status telemetry (#688)

* feat(opencode): support plan mode

* feat(opencode): support reasoning effort

* feat(opencode): surface context usage in web

Bridge OpenCode ACP usage updates into the existing token-count pipeline so the web status bar can show live context and cache information without a separate UI path.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(opencode): restrict plan mode to remote, rollback reasoning effort on failure

- Block local OpenCode plan startup (tools not enforced in local path)
- Allow remote OpenCode plan only (ACP permission handler denies tools)
- Guard web /permission-mode endpoint for local OpenCode plan sessions
- Rollback session reasoning effort when OpenCode rejects set_config_option
- Wire rollback callback through opencodeLoop to runOpencode closure
- Add tests: local plan rejected, remote plan allowed, web guard, effort rollback

* fix(web): auto-retry OpenCode models query to populate model selector without refresh

- Retry early failures (RPC may still be registering on new sessions)
- Poll briefly until availableModels is non-empty
- Stop polling once model options are discovered
- Add tests for retry/poll/stop policy

* fix(opencode): cap model discovery polling

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/hooks/mutations/useSessionActions.ts

@@ -106,11 +106,11 @@ export function useSessionActions(
             if (!api || !sessionId) {
                 throw new Error('Session unavailable')
             }
-            if (agentFlavor !== 'codex') {
-                throw new Error('Model reasoning effort is only supported for Codex sessions')
+            if (agentFlavor !== 'codex' && agentFlavor !== 'opencode') {
+                throw new Error('Model reasoning effort is only supported for Codex and OpenCode sessions')
             }
-            if (!codexCollaborationModeSupported) {
-                throw new Error('Model reasoning effort is only supported for remote Codex sessions')
+            if (agentFlavor === 'codex' && !codexCollaborationModeSupported) {
+                throw new Error('Model reasoning effort is only supported for remote sessions')
             }
             await api.setModelReasoningEffort(sessionId, modelReasoningEffort)
         },