feat(v0.7.50): add same-repository content and evidence

[qiansc]

Summary

• Add same-repository documentation and authored Skill registration, derived symlink entrances and safe repair guidance.
• Preserve historical evidence paths, detect document-region and Skill-directory changes, and support repository evidence in the bundled Wasm plugin.
• Add optional repository entrance pages and adapt local/remote query skills without copying source documents into knowledge.
• Release 0.7.50 and refresh workspace lock and generated plugin projections.

Validation

• Workspace build and frozen dependency installation passed.
• Targeted repository-content tests passed (17 tests), including real Node CLI status and failed-build output preservation.
• Full release validation found missing guide packaging and an unclassified historical path; both were fixed. A manual-link test was updated to distinguish URI links from local files. Targeted recheck passed (9/9), remaining full-only tests passed (39/39), and Node distribution plus CLI artifact tests passed (2/2).
• Source audit found no internal business identifiers or private service domains.

Merge is reserved for the maintainer. Release is handled separately.