docs: fix stale documentation drift (roadmap, workspace tree, Starlight to Nimbus)

[amondnet]

Context / Motivation

Several docs describe a state of the project that no longer matches the code. Each item below is a concrete, verified drift — this is a mechanical cleanup, not a docs rewrite.

Proposed scope

• README.md:337-359 — the roadmap still lists RSS/Atom as pending, though it shipped in feat(web): add RSS and Atom incident-history feeds #41, and omits Cloudflare Queues delivery, which shipped in feat(worker): optional Cloudflare Queues path for reliable notification delivery #43.
• README.md:137-149 — the workspace tree lists only apps/web, apps/worker, and packages/core; it is missing apps/docs, packages/cli, and packages/create-statusbeam.
• ARCHITECTURE.md:88-99 — the module table has the same omission as the workspace tree.
• ARCHITECTURE.md:220-223 — states Queues are not wired, but apps/worker/src/index.ts:20-26,58-60 and packages/core/src/config.ts:109-133 implement the Queues path.
• .github/workflows/deploy-docs.yml:3 — the workflow name says "Starlight", but apps/docs runs on @cloudflare/nimbus-docs (since commit 1acfc58).
• docs/adr/index.md:4-9 — lists ADR-0002 as Proposed, while the ADR body itself says Accepted.
• .please/docs/knowledge/tech-stack.md:52-56 — says Queues are planned, though they are implemented.

Acceptance criteria

• Every item above is corrected and matches the code at the referenced locations.
• No other documentation content is changed as part of this issue.

Priority / Effort / Dependencies

• Priority: p2
• Effort: S (<1 day)
• Dependencies: none.