* docs(parity): review upstream release 0.69.0

Official CodexBar 0.68.0 and 0.69.0 keep the 87-provider registry with the
same records and add no CLI flags or JSON envelope changes. Probes against
the checksum-verified official Linux assets, run under bubblewrap isolation
with synthetic inputs, verify the Mistral manual-cookie runtime fix before
and after (0.67.0 refuses as macOS-only, 0.68.0+ attempts the fetch),
unchanged setup reachability for the bundled-plugin migrations, the still
year-1 --period all day count, and empty-config tolerance.

Documentation impact: adds and indexes the dated 0.69.0 review, moves the
TODO baseline to 0.69.0, records the Mistral cookie writer gap, rechecks
the descriptor, config-action, Cursor cost, and display-currency blockers,
adds a Mistral allowance-window verification candidate, folds the
Antigravity Starter quotas into the quota-window candidate, and refreshes
the registry pins in README and the usage guide plus the All-history
evidence in the cost guide.

* docs(parity): track rejected API-key setup and clarify Abacus probe

Codex review notes that released CLI 0.69.0 rejects set-api-key for
mistral and abacusai while the frontend still offers the action. That
removal is implementable frontend work, so track it in TODO with evidence
and a done condition instead of leaving the section empty.

Also clarify that the Abacus reachability row comes from a re-run with
the accepted abacusai argument; the discarded abacus invocation only
documented the CLI fallback quirk.