release: v0.9.0, and rewrite FUTURE.md around what is actually planned

FUTURE.md had become a 648-line archaeological record: six shipped roadmap
items, two dropped, two implemented, an investigation trail for each, and a
backlog closed as not needed — with the two genuinely planned items buried
at the bottom. It is now 139 lines, planned work first.

- Archives the old file verbatim as FUTURE-ARCHIVE.md. It carries the recon
  behind decisions now recorded in one line each — why Brave cookie
  extraction is not viable, why the ChatGPT token's expiry cannot be read
  client-side, how the drift canary was designed — which would be expensive
  to rediscover.

- Roadmap is now two items: the StartOS service (including the 2026-08-18
  decision that clients upload to StartOS storage and the service owns the
  Joplin connection), and the README split.

- Everything shipped or dropped is off the roadmap. Decisions not to build
  survive as a one-line table so they are not re-proposed.

- Status notes for v0.7.0 and v0.8.0 move into Completed, joined by v0.9.0.

Releases v0.9.0: pyproject 0.8.0 -> 0.9.0, and the changelog's [Unreleased]
section becomes [0.9.0] - 2026-08-18. Covers the Codex provider, the
launcher scripts, `sync`, daily scheduling on Linux and Windows, ntfy
notifications, gizmo_id project attribution and the `projects` command, and
the splitlines data-loss fix in both local providers.

Whitelists FUTURE-ARCHIVE.md in .gitignore. `*.md` is ignored on purpose —
exported conversations are Markdown and may contain private content — with
each doc re-included by name, so a new doc is silently untracked rather than
rejected. The archive would not have been committed at all. Recorded in the
README-split roadmap item, since `docs/*.md` will hit exactly this.

Also refreshes the package description, which still named only ChatGPT and
Claude after two local providers were added.

Carries the documentation and table-of-contents work from earlier today.

.gitignore

@@ -22,6 +22,7 @@ exports/
 !tests/fixtures/*.json
 !README.md
 !FUTURE.md
+!FUTURE-ARCHIVE.md
 !CHANGELOG.md
 
 # Cache and logs