chore(release): prepare agent-knowledge 7.0.0

[drewstone]

Release

Publishes the exact-source claim ledger contract merged in #101 as a major release.

Breaking changes:

• commitSources now confirms SourceRecord values instead of URI strings
• durable claim ledgers use schema version 2 with source id, original URI, and SHA-256 content hash
• URI-only 6.2 ledgers fail closed and remain untouched for explicit archive and re-verification

Local release proof:

• 518 tests passed; 12 skipped integration tests
• lint and typecheck passed
• build, publint, packed type checks, and clean-package lifecycle passed
• official GEPA and SkillOpt packed-package verification passed