rename: opencortex → passepartout across memex

- .gitmodules: update submodule paths (projects/opencortex → projects/passepartout,
  projects/opencortex-contrib → projects/passepartout-contrib)
- gtd.org, README.org: update project references and display names
- check.lisp, gemini-vision.org, agora/TODO.org: update file paths
- dotemacs: update agenda paths and template config
- system/plans/: update all flight plan references
- system/backups/: update monolithic backup references

system/plans/flight-plan-chat-ui-fix.org

@@ -10,7 +10,7 @@ The user is seeing the agent's meta-commentary (e.g., "Okay, I've inserted...")
 
 ** Coder Phase
 - [X] Create =inbox/flight-plan-chat-ui-fix.org= (this file).
-- [ ] Update =projects/opencortex/src/opencortex.el= to replace "Thinking..." lines.
+- [ ] Update =projects/passepartout/src/opencortex.el= to replace "Thinking..." lines.
 - [ ] Update =notes/org-skill-chat.org= to suppress conversational preamble.
 - [ ] Tangle and restart.