fix: harden work graph input validation

[Gandy2025]

Summary

• require schema_version to be the JSON integer 1
• reject blank work-item titles and source references
• fail closed when a local ticket omits its Blocked by declaration
• update the local-ticket fixtures and public English/Chinese contract documentation

Why

The validator previously accepted schema_version: true because Python
booleans compare equal to integers, and required string fields could still be
blank. The local builder also treated a missing blocker declaration as an empty
dependency list, which could release a malformed ready ticket.

The tightened behavior requires local tickets without dependencies to declare
that state explicitly, normally with Blocked by: None.

Impact

Malformed normalized manifests and incomplete local tickets now stop before
dispatch instead of entering the current frontier. Existing valid to-tickets
v1.2.2 artifacts already contain an explicit blocker declaration.

Validation

• python3 scripts/validate_skills.py
• python3 -m unittest discover -s tests — 83 tests, 1 filesystem-dependent skip on macOS
• python3 evals/floor.py — 5/5 PASS
• python3 -m compileall -q scripts skills tests evals
• uvx ruff check .
• uvx ruff format --check .
• uvx --from skills-ref agentskills validate skills/run-with-first-tree
• npx --yes skills@1.5.22 add . --list
• npx --yes skills@latest add . --list
• git diff --check