Add Claude Code integration through the shared memory CLI

[bfirestone]

Add Claude Code as the second client of the shared Observational Memory CLI after the Codex-first release.

• Verify Claude Code's current lifecycle event and response contracts against its official documentation.
• Implement a separate client adapter that reuses the existing SQLite ledger, checkpoint, reflection, retirement, and recall operations.
• Add the Claude-specific skill, hook registration, installer, and integration tests to agent-marketplace, keeping the runtime source here.
• Preserve explicit session/store selection, evidence provenance, bounded context, and stop-recursion protection.
• Pin and test a compatible CLI release in each marketplace plugin. Keep standalone self-update from replacing plugin-managed binaries.

Acceptance: synthetic end-to-end Claude lifecycle tests pass, Codex behavior remains covered, and the core does not depend on either client's event fields.