chore(release): prepare 2026.07.1

[tcballard]

Prep for the 2026.07.1 release (CalVer, ADR-076). Bumps package.json 2026.06.0 → 2026.07.1 (zero-padded; the release workflow de-pads to 2026.7.1 for npm) and adds a CHANGELOG entry — the "any model" release — covering everything merged since 2026.06.0:

• OpenAI-compatible adapter — BYOK for any model (OPENAI_API_KEY / OPENAI_BASE_URL / OPENAI_MODEL), no new dependency.
• Browser-extension verification — --extension <dir> / per-env extensionPath; loads the extension, drives it, compiles a spec that re-loads it and re-resolves the runtime ID.
• Dogfood self-coverage gate + badge — CI fails if any of Proofkeeper's own capabilities is unverified.
• Graph schema_version guard — refuses an unsupported rac export --graph version with a clear error.
• Trusted Publishing (OIDC) — tokenless npm publish with automatic provenance.

Docs/metadata only — no code change.

Release steps (tomorrow)

1. Merge this PR.
2. Cut a GitHub Release tagged 2026.07.1 (zero-padded, matching package.json).
3. The release workflow verifies tag == package.json, de-pads to 2026.7.1, builds, and publishes to npm via OIDC with provenance.

Reminder: the npm Trusted Publisher must be configured for @itsthelore/proofkeeper (org itsthelore, repo proofkeeper, workflow release.yml) before the OIDC publish will succeed.