Implement skills REST handlers with project_root

[JAORMX]

Summary

• implement skills REST handlers behavior for list/install/uninstall/info (query + payload parsing) with client and project_root
• enforce strict project_root validation (absolute path, exists, directory, no traversal/null bytes, git repo) at API and service layers
• normalize project_root to keep DB records and locks consistent across equivalent paths
• update handler and service tests to cover project_root validation failures and successful flows
• regenerate swagger docs to reflect the new parameters

Rationale

• issue REST API skills handlers #3651 is about completing the REST handlers; this change wires the query/payload params and error handling expected by the handlers
• project_root is sensitive: without validation it can enable path traversal or arbitrary filesystem access; validating at both API and service layers prevents misuse from any entry point
• requiring git roots keeps “project” scoping aligned with the intended workflow and reduces accidental use of unrelated directories
• normalizing project_root avoids duplicate records for the same directory and prevents lock key mismatches

Issue

• resolves REST API skills handlers #3651

Reviewer Notes

• expect new 400s when scope=project is used without project_root, or when project_root fails validation
• list/install/uninstall/info now accept project_root; list also accepts client
• docs are regenerated in docs/server/*

Testing

• task test
• task docs

[codecov]

Codecov Report

❌ Patch coverage is 90.16393% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.83%. Comparing base (a7ec95a) to head (3c4a0b2).
⚠️ Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/skills/project_root.go	83.33%	8 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3911      +/-   ##
==========================================
+ Coverage   67.76%   67.83%   +0.06%     
==========================================
  Files         439      440       +1     
  Lines       44130    44229      +99     
==========================================
+ Hits        29905    30001      +96     
- Misses      11881    11885       +4     
+ Partials     2344     2343       -1     

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[JAORMX]

@claude could you fix the listing errors?

[claude]

Claude encountered an error —— View job

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I'll analyze this and get back to you.

[aponcedeleonch]

looks good

[jhrozek]

LGTM — solid validation with good defense-in-depth. One minor nit left as an inline comment.

[aponcedeleonch]

LGTM