fix(skills): validate frontmatter name matches directory name at write time

[liuhao1024]

What does this PR do?

_create_skill() and _edit_skill() silently accept content whose frontmatter name differs from the name parameter (the directory name). This creates skills whose skills_list display name diverges from the directory name used by skill_view(), making them permanently undiscoverable.

Root Cause

Neither _create_skill() nor _edit_skill() validates that the YAML frontmatter name field matches the name parameter. The write path accepts any valid frontmatter, creating a directory named after the name parameter while storing a different name in the SKILL.md frontmatter.

• skills_list() → returns frontmatter name (e.g., local-paper-summary)
• skill_view("local-paper-summary") → resolves by directory name → not found

Related Issue

N/A

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• See commit messages for detailed changes

How to Test

1. Run pytest tests/ -q — all tests should pass
2. Verify the specific scenario described above is resolved

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 26.4.1

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture and workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A

[teknium1]

Thanks for identifying the write-time namespace invariant; it is still absent on current main. The original discoverability symptom is mitigated by the later frontmatter-name lookup in tools/skills_tool.py:1155-1170, but enforcing a single write-time identity remains useful.

Problems

• The skill change covers create/edit only. _patch_skill() still accepts a changed name: after calling _validate_frontmatter(new_content) at tools/skill_manager_tool.py:997-1004, so it can recreate the divergent state.
• The bundled PATCH_SCHEMA change is incompatible with its mode-specific handler: mode="patch" consumes only patch at tools/file_tools.py:1841-1844, while current tests deliberately keep JSON-schema required to ['mode'] at tests/tools/test_file_tools.py:594-613.
• The WhatsApp environment-variable commit is unrelated to this skill fix and conflicts with the config.yaml convention in AGENTS.md:102-106.

Suggested changes

• Salvage the skill-only change against the current _validate_frontmatter() implementation and apply it to create, edit, and SKILL.md patch writes.
• Add the missing patch regression and retain the existing content on rejection.
• Split out the unrelated commits.

This is an automated hermes-sweeper review.