fix: encode branch names in GitHub links

[Abdullah-Builds]

Encode branch names in GitHub links

Closes #1712

Summary

Fixes GitHub branch and compare links generated by the action when a valid branch name contains URL-significant characters such as #.

Branch names are now encoded one path segment at a time, so / remains a branch hierarchy separator while # is encoded as %23 instead of becoming a URL fragment.

Changes

• Add encodeBranchNameForUrl() for Git-ref URL paths.
• Use it for tracking-comment branch links and fallback branch links.
• Use it for generated pull-request compare URLs.
• Add a regression test for claude/fix#123.

Example

Before:

https://github.com/owner/repo/tree/claude/fix#123

After:

https://github.com/owner/repo/tree/claude/fix%23123

Validation

• git diff --check
• Added regression coverage in test/comments-common.test.ts

Note: The local environment does not have Bun installed, so the Bun test suite could not be run here.