fix(skills): resolve skill_view by frontmatter name when dir name differs

[kshitijk4poor]

Summary

Allow skill_view to resolve a skill by its frontmatter name: when the on-disk directory name differs.

skills_list() surfaces each skill's frontmatter name:, but skill_view() previously only matched on the on-disk directory name (Strategy 2). When a skill's directory is a shorter category/alias that differs from its frontmatter name, skill_view(name) failed to find it. The recursive Strategy-2 walk now also matches frontmatter name:, guarded by a try/except so an unreadable/malformed SKILL.md can't break discovery.

Context

This is a single-concern salvage of one part of #39682, lifted onto current main. The original PR shipped this change without a test; this PR adds one. The other concerns in #39682 are already resolved upstream (Desktop dist/** and nested-category plugin discovery both landed on main separately), and the Langfuse data-URI fix from that PR is sent as its own PR.

Test Plan

venv/bin/python -m pytest tests/tools/test_skills_tool.py -q

• 87 passed (adds test_view_skill_by_frontmatter_name_when_dir_differs).
• RED-GREEN verified: the new test fails on current main (skill not found) and passes with this change, proving it exercises the new frontmatter-name lookup path.
• ruff check clean on touched files.

Co-authored-by: foras910521-lab foras910521-lab@users.noreply.github.com

[alt-glitch]

Duplicate of #30906 — same skill_view frontmatter-name fallback fix in tools/skills_tool.py. This is part of a saturated cluster: #17918 and #18879 (closed), #18901 and #28305 (still open), all targeting root issue #17914. The canonical open PR is #30906; this one adds a test (which #30906 lacks), so the test may be worth salvaging into the canonical PR. Consolidation needed across the chain.