Add legacy redirect for session files and fix STL viewer error handling ...

- Add /sessions/{id}/files/{filename} → /api/sessions/{id}/files/{filename}
  redirect in main.py for backward compatibility with old persisted URLs
- Fix STL viewer: wrap all renderer-dependent code in `if (renderer)`
  to prevent cascading errors when WebGL is unavailable
- Rebuild dist

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Fix SyntaxError: Illegal return statement in STL viewer ...

The previous fix replaced `throw err` with `return` inside a module,
but top-level `return` is a SyntaxError in ES modules.
Reverted to `throw err` — the error message is already shown on screen,
so the user still gets a graceful fallback even though the error appears
in the console.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Fix session file URLs (add /api prefix) and WebGL error handling in STL viewer ...

Backend:
- _file_url in content_store.py now returns /api/sessions/... instead of /sessions/...
- share_file.py URL construction updated to include /api
- content_publish.py docstring updated to reflect correct endpoint

Frontend:
- contentLinks.js: avoid double /api prefix in dev mode when backend already returns it
- stl.html: replace throw err with return after showing WebGL fallback message
- Rebuild dist

Tests:
- Update expected URLs in test_content_store.py and test_share_file.py

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Extract ContextCompressor, fix STL viewer, expand test suite, add architecture audit docs ...

- Extract ContextCompressor from agent.py (Step 1 of god-object refactor)
- Add retry + hard-truncate fallback logic to ContextCompressor
- Add unit tests: agent loop (14), compressor (18), KV store (8),
  auth encrypt (3), auth deps (13), todo/scratchpad/image_view/memory
- Fix WebGL STL viewer: allow-same-origin sandbox + graceful fallback
- Add CompressionStarted event and client-side compression notice
- Add docs/architecture_weak_spots.md and plan_01_god_object_agent.md
- Update test_events.py and test_agent_context_size.py for new logic

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Improve artifacts workspace controls

Add artifact source previews

Restore original scrollbar appearance

Normalize scrollbar styling

Improve content publishing UX

Fix system prompt leakage into chat history; polish content cards ...

Backend:
- websocket.py + agent.py: separate user-visible display_message from
  LLM user_message. System hints (image/file attachments) no longer leak
  into session.messages and appear after page reload.
- main.py: add ensure_tables() on startup so session_content table is
  created before first publish.
- profiles: add kimi-k2.6:cloud to all model lists as fallback.

Frontend:
- ContentCard.vue: remove border-radius, add scrollbar styles, fix
  metadata fallback parsing so cards survive page reload.
- content-viewers/*.html: add matching scrollbar styles.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Add content hosting system with inline viewers ...

Backend:
- Add navi/content/ directory for published files
- Add content_store.py with publish/list/delete/cleanup functions
- Add content_publish tool for publishing files as viewable content
- Add /content static file mount in main.py
- Add /content-viewers mount for viewer pages
- Extend ToolEvent with metadata field
- Forward metadata through websocket tool_call events
- Update Agent to include metadata in ToolEvent

Frontend:
- Add ContentCard.vue component for displaying published content
- Add viewer pages: stl.html (Three.js), svg.html, html.html, pdf.html
- Update AssistantMessage.vue to render ContentCard for content_publish
- Update chat store to preserve metadata in tool cards
- Update websocket protocol docs with metadata field

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Migrate to Vue webclient; rename old client to old_webclient ...

- client/ → old_webclient/ (vanilla JS client preserved as reference)
- webclient/ — new Vue 3 + Pinia webclient (source + dist build)
- vite.config.js: outDir changed to webclient/dist/
- main.py: serve /assets and /images from webclient/dist/,
  index.html from webclient/dist/index.html
- .gitignore: exclude webclient/node_modules/, include webclient/dist/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>