Fix project pin discovery for glob metacharacters in project paths #1808

Problem

dispatcherPinCandidatePaths in cli/dispatcher/internal/dispatcher/dispatcher_pin.go uses filepath.Glob for PackageCache pin discovery. If the Unity project path contains glob metacharacters such as [ or ], the project-root portion is interpreted as a pattern and valid pin candidates can be missed.

The V2 package detector no longer has this issue because it uses os.ReadDir, but the existing V3 project-runner pin path still does.

Reproduction

1. Create or move a pinned V3 Unity project under a path such as <PROJECT_ROOT>/project[legacy].
2. Ensure the package pin is available through Library/PackageCache/<PACKAGE_NAME>@*/project-runner-pin.json and no higher-priority copied pin is present.
3. Run a project-scoped uloop command.
4. Observe that pin resolution can report the pin as missing.

Expected

PackageCache discovery treats every project-root character literally and finds the pin regardless of glob metacharacters.

Suggested direction

Replace the glob-based directory discovery with literal os.ReadDir traversal, matching the V2 detector approach, and add regression coverage for bracketed project paths and Windows separators.