docs: fold the workspace-root docs into the repo, with honest status

The root held four Markdown files that were not in any git repo and were being read as
current. CLAUDE_SIDECAR_ISOLATION.md is the one that prompted this: it describes, in the
present tense, an agent that dies whenever officer restarts. That was true when it was
written and has not been true for two days.

Rather than delete analysis that version control was not holding, the two substantial ones
moved into platform/docs/ with headers that say what has since happened:

- claude-sidecar-isolation.md — stages 0-2 are done and running (R1, R2, R4, R5 all
  satisfied); stages 3-5 are the only live part.
- sidecar-audit-2026-07.md — a snapshot audit, largely executed. Email, pty, music and vnc
  have been done since; claude, opencode and the cross-cutting notes are still open. The
  vault stays off-limits.

MUSIC_IMAGES_SPEC.md is deleted outright: the sidecar serves /image and /poster, so the
spec is the feature. The workspace root now holds one Markdown file, CLAUDE.md, which is
where cross-cutting operational reality belongs.

Also corrected, in the same pass:
- root CLAUDE.md listed email as "the big one, and untouched" and pty stage 4 as
  outstanding; both are done. It now names what actually remains (claude stages 3-5, the
  terminal orphan leak) and what landed.
- docs/sidecar-topology.md said "nothing built yet". Two sidecars now serve their own
  transport; what has NOT happened is the part the document is about — fixed ports, the
  shared table, .env toggles — so it says exactly that rather than implying the design is
  underway. Migration order updated: pty and email went first, not music.
- docs/navigation-audit.md is cited as authoritative but still planned work on Projects,
  a feature since deleted. A status header marks H3 void, H1/H2 done and H4 the one open
  item, so nobody follows it into a directory that no longer exists.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/navigation-audit.md

@@ -1,6 +1,14 @@
 # Frontend Navigation Audit — the "opaque click" anti-pattern
 
-**Date:** 2026-07-30 · **Branch:** `sidecars-claude` · **Status:** exploration + documentation only (no code changed)
+> **Status, 2026-07-31.** H1 (jobs), H2 (dashboards) and H4's groundwork are **done** — rows are real
+> `<Link>`s and selection lives in `?selected=` / `useParams`. **H3 is void: the Projects feature was
+> deleted**, so every reference to `Projects/`, `SELECTED_PROJECT` and `/projects/:id` below is historical
+> and should be read as an example of the pattern, not as work to do. **H4 (chat detail reading
+> `sessionId` from `useParams` rather than the `chat:selected-session` channel) is the one item still
+> open.** The rules in this file are current and authoritative; the findings table is a snapshot.
+
+
+**Date:** 2026-07-30 · **Origin:** written as exploration before any of the routing work was done.
 
 Prep work for the upcoming **full navigation refactor**. This catalogues every place the frontend
 navigates to / selects an **addressable entity** using a `<button onClick>` / `<div onClick>` /