Prepare v1.15.0 Usage retirement release

[sarthakagrawal927]

Purpose

Prepare v1.15.0 as the lean release for retiring general agent Usage. The desktop Usage workspace and ccusage sidecar were removed on main in #331 and #329. This branch synchronizes the native and Rust versions, gives callers of codevetter usage and codevetter quota a short ContextDaddy migration message, and records the release boundary in product docs.

User-visible change

• General agent usage and allowance tracking moves to ContextDaddy.
• codevetter usage and codevetter quota return a migration error. There is no equivalent ContextDaddy CLI command today.
• Per-verification token and cost receipts, and CodeVetter's local History recovery, remain.

Qualification

• Exact PR head bbe740c3: all required checks passed, including Linux CI, Rust, Swift CodeQL, hosted native tests, isolated desktop interaction, package inspection, docs, and security checks.
• Protected production-candidate run passed at the same head: Developer ID signing, Apple notarization and stapling, archive binding, Sparkle signature, retained-release migration, relaunch, custom rubric/data preservation, rollback, and production readiness contracts. It uploaded the candidate evidence without publishing a release.
• A local integration merge with current main (9a6024c6, including the inspiration series and Starboard cross-link) is conflict-free. pnpm version:check, pnpm build:landing, docs validation, and agent-surface validation pass; all 871 generated routes have Markdown and API catalog coverage.
• pnpm core:test, pnpm core:clippy, pnpm core:qualify-cli, cargo fmt --check, lint, docs validation, and secret scan passed locally before the exact-head CI.

Release boundary

Keep this PR in draft until the owner approves publishing v1.15.0. Merging the version bump to main triggers auto-release.yml, which creates the signed and notarized public release. After publication, verify the release manifest and public assets, update PROJECT_STATUS.md from candidate to published truth, redeploy the landing page, and smoke /download, /docs, and /inspiration so the app and site match.

The live site currently serves v1.14.3 on /download, while its newly deployed docs describe the pending Usage removal. Do not present the app and docs as synchronized until v1.15.0 is public.

Tracks #328.