docs: remove code-review.md, carry the open items into roadmap

The review's plan is finished — phase 0 (bar the two release-commit steps),
1, 1.5, 2 and 3 are all closed — and what remained in the document was a second
copy of things that already live in architecture.md, security.md, roadmap.md or
the code comments: the GUI compromise table is in panel.css/panel.js/
middleware.go/handlers_auth.go, the single SQLite connection and the dual
cookie names are explained where they are implemented, the accepted gaps are in
security.md, and the model-routing table names progress.md and development.md
as its own source. A second copy of a fact is a place for it to go stale.

Four items were genuinely open and had no other home, so they moved to
roadmap.md rather than disappearing:

- splitting internal/web into subpackages (2.x) — with the reason to wait: the
  flat package still reads at 47 files, and both 2.x features grow it, so the
  cut is worth making before that growth, not now;
- a consolidated documentation index in the README (v1.x tail);
- the adaptive polling interval for a tab that is visible but idle — the hidden
  case is already handled, and the remainder is explicitly allowed to end as
  "decided not to";
- CONTRIBUTING.md, already moved to 2.x in the previous commit.

References retargeted: progress.md (7), roadmap.md (5), implementation-plan.md
(1). The CHANGELOG entries that cite the document are left as written — they
describe what happened at the time. The review text stays in git history at
522425a.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -44,6 +44,14 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
   live document that owns the subject — `docs/architecture.md` (with section),
   `docs/product.md`, `docs/security.md`, or the README. Comments only; no
   behaviour is affected.
+- `docs/code-review.md` is gone. Its plan is finished — phases 0 (bar the
+  release-commit steps), 1, 1.5, 2 and 3 are all closed — and the rest of the
+  document had become a second copy of what `architecture.md`, `security.md`
+  and the code comments already say. What was genuinely open moved to
+  `docs/roadmap.md`: splitting `internal/web` into subpackages, a consolidated
+  documentation index in the README, the adaptive polling interval for an idle
+  but visible tab, and `CONTRIBUTING.md`. The review text stays in git history
+  (`522425a`); the CHANGELOG entries below that cite it are left as written.
 - `docs/architecture.md` gained a *Code layers* section: a diagram of
   handlers → services → store plus the adapters, and the reason the services
   layer exists (multi-store writes and their rollback) — closing item A2 of