docs: split CLAUDE.md into root, src/web/CLAUDE.md and docs/releasing.md

The root CLAUDE.md had grown to 202 KB, all of it loaded into every
session. This lands the split drafted on 2026-10-10 (it sat uncommitted
in the shared checkout through two releases), redone on top of today's
master so nothing that landed since is lost:

- src/web/CLAUDE.md: the frontend invariants (every src/web/public/ UI
  subsystem, the module notes, the XLSX preview limits, the z-index
  stack). Claude Code loads it when a file under src/web/ is read; the
  root file tells sessions to Read it before editing src/web/public/.
  Its link targets are relative to the file so they resolve on GitHub.
- docs/releasing.md: the COM procedure (now nine steps, with the MCP
  registry publish), behind a pointer in the root COM section. The
  Version line stays in the root file.
- Root CLAUDE.md (130 KB): everything else, plus the split's trims: the
  Core Files table, the reference-only rows of the Additional Commands
  table, Data Flow and the respawn presets, whose rules already live in
  the root's other paragraphs (the "Read before touching a subsystem"
  line keeps the table's doc pointers).

Every other paragraph of master's CLAUDE.md lands in exactly one of the
three files, checked line by line; the paragraphs master changed since
the draft (tile grid, OSC 52, prompt uploads, file-path links and the
HTML view, markdown preview, z-index, MCP server, agent CLI and others)
are in their current form. Both new files join CLAUDE.md in
.prettierignore. Four code comments and docs/architecture-invariants.md
now point at src/web/CLAUDE.md for the moved sections.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/custom-model-run-menu-ui.test.ts

@@ -745,7 +745,7 @@ describe('Custom Model Endpoint Profiles: applying a picked entry', () => {
   });
 
   it('routes through run() itself, so the Run in-flight lock actually engages', async () => {
-    // CLAUDE.md, Run launch synchronization: the lock exists so a double click
+    // src/web/CLAUDE.md, Run launch synchronization: the lock exists so a double click
     // cannot create duplicate sessions. A hardcoded dispatch table bypassing
     // run() would never set _runInFlight, which is what this pins.
     const { app } = bootApp({});