docs(debug-playbook-engine): make canMakeClaim example actually run

[LanNguyenSi]

Refs agent-tasks b1d8a15c-d683-49c8-b0f4-534c54b84c32.

Why

The README API snippet at packages/debug-playbook-engine/README.md:65-75 looked like a happy-path tutorial for canMakeClaim, but the call it makes (canMakeClaim(state, 'root-cause') after recording check-repo-model + check-agent-process) is unsatisfiable: root-cause requires read-docs + check-process, neither of which exist in the clawd-monitor playbook. A reader who copy-pasted the snippet got { allowed: false } and the opposite of the lesson the prose was teaching.

What changed

packages/debug-playbook-engine/README.md only. The new example demonstrates both states of the gate, end-to-end:

1. After check-repo-model + check-agent-process, canMakeClaim(state, 'config') correctly blocks with reason: ['Required step not completed: check-config'].
2. After walking through check-start-mode (mandatory order enforced by recordStep) and then check-config, canMakeClaim(state, 'config') returns { allowed: true }.

Also added a closing paragraph naming the unsatisfiability of root-cause and architecture under non-generic playbooks. That is a real defect in canMakeClaim's requirements table (its step IDs are scoped to the generic playbook even though it accepts state from any playbook), but it is out of scope for a README PR. Worth filing as a follow-up if you want it addressed.

Out of scope

• The sibling finding from the audit (grounding-wrapper README importing handleScopeChange) turned out to be a false positive: lib.ts:236 exports handleScopeChange, and package.json main resolves to dist/lib.js, so the snippet on master already works. No grounding-wrapper change in this PR.
• Six .version("1.0.0") lies across sibling packages: covered by separate sweep task 163a2845.

Verification

Ran the new example verbatim against dist/lib.js:

blocked: {"allowed":false,"reason":["Required step not completed: check-config"]}
allowed: {"allowed":true}

• npm test (debug-playbook-engine): 21 / 21 jest green.
• npm run typecheck (debug-playbook-engine): clean.
• slop-detector clean on commit message.

Test plan

• Review subagent confirms the new snippet runs as documented against current lib.ts.
• Reviewer agrees that the closing "unsatisfiability" paragraph is the right place to mention the root-cause / architecture mismatch (vs. filing a code follow-up as the primary action).
• CI green.