pre-commit: check-vcs-permalinks fails on non-permalink GitHub URLs in docs

[scottschreckengaust]

Part of #213.

Problem

check-vcs-permalinks fails because docs link to mutable .../blob/main/... GitHub URLs instead of commit-pinned permalinks. These links rot when the target repo's main moves.

Affected lines

plugins/databases-on-aws/skills/dsql/mcp/tools/input-validation.md:56
plugins/databases-on-aws/skills/dsql/mcp/tools/input-validation.md:61
plugins/databases-on-aws/skills/dsql/mcp/tools/database-tools.md:125

All point at https://github.com/awslabs/mcp/blob/main/src/aurora-dsql-mcp-server/....

Reproduce

mise exec -- pre-commit run check-vcs-permalinks --all-files

Proposed fix

Replace blob/main/ with a commit SHA permalink (on GitHub, press y on the file view to get one), or if a moving reference is intentional, exclude these specific docs from the hook.

_{Filed with assistance from Claude Code while implementing #211.}