Add Standalone Login Page Renderer

Add a hash-bound, no-store login document with focused C and Node host
tests. Keep rendering inert until the 8D.3 authentication cutover.

docs/agent/code-map.md

@@ -71,6 +71,7 @@ This is a semantic map, not a complete file inventory. Start here, then read the
 - Security constraints: Basic-auth cache hits still revalidate principal currentness; the browser's combined Connect/Disconnect control closes the WebSocket and pauses automatic reconnect until Connect is selected. Changes to the authored inline loader must update its hard-coded CSP hash in the same change.
 - Session-store boundary: admitted HTTPS start initializes four static records; failed start/accepted stop disables and wipes them. 8D.2 binds tickets/slots to non-reused session IDs (zero only for Basic); transport-specific cleanup and account/global revocation invalidate store records before socket cleanup. No cookie route yet. RNG/SHA/database calls run outside short portMUX sections; ID/expiry/epoch checks reject stale work. Run `python3 tests/web_session_store/run.py` and its `--serial` integration mode.
 - 8D.3 preparation: `src/web_auth_parse.{c,h}` provides inert, allocation-free origin/cookie/login-JSON parsing; no HTTP caller yet. Test with `python3 tests/web_auth_parse/run.py`. These helpers do not authenticate or replace HTTP header/method/CSRF policy.
+- 8D.3 login rendering: `src/web_login_ui.{c,h}` contains a standalone no-store login document and hash-bound script; no registered route or live caller. `python3 tests/web_login_ui/run.py` checks production C rendering, CSP and Node DOM/fetch doubles. Existing `web_ui.c` and generated assets are unchanged.
 - Asset constraint: `web_assets_data.c` is checked-in generated input to the build; do not hand-edit or regenerate casually.
 
 ## SSH