fix(skills): fall back to junctions for Windows skill links

[TheLonelyDevil9]

What?

Adds a Windows fallback for skill sync when directory symlink creation fails. CC Switch now treats skill sync links as managed links: Unix symlinks, Windows directory symlinks, or Windows junctions.

Why?

Non-admin Windows sessions without Developer Mode can fail directory symlink creation with an administrator-privilege error. That breaks live skill sync across CLI harnesses and can remove an existing link during toggle/re-sync flows.

How?

• Keeps Unix symlink behavior unchanged.
• Tries std::os::windows::fs::symlink_dir first on Windows.
• Falls back to an NTFS junction using CreateFileW and DeviceIoControl(FSCTL_SET_REPARSE_POINT), avoiding cmd.exe/mklink shell parsing.
• Detects Windows directory reparse points as managed skill links.
• Removes managed links without recursively deleting the target directory.
• Normalizes Windows link targets with \??\ / \\?\ prefixes before SSOT comparisons.
• Updates skill sync tests to validate live managed-link behavior and orphan cleanup through the public sync path.

Testing?

• git diff --check
• Manual Windows validation: junctions work in the affected non-admin session where symlink creation fails.
• Not run locally: cargo fmt, cargo test, or Rust build checks because Rust tooling is not available in this shell.

Screenshots (optional)

Not applicable.

Anything Else?

No matching open upstream PR was found for Windows skill symlink-to-junction fallback.

[farion1231]

@codex review

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restrict managed-link detection to symlink/junction tags

The Windows managed-link check currently treats any directory with FILE_ATTRIBUTE_REPARSE_POINT as a CC Switch link, but many non-link directory types (for example cloud placeholders or other reparse-tagged directories) also match this predicate. Those paths are then routed through remove_path() as managed links, which uses remove_dir instead of recursive removal; this can fail on non-empty directories and break sync/remove flows when a normal skill directory carries a non-symlink reparse tag. The check should validate the reparse tag (e.g., only symlink/mount-point junction tags) before classifying a path as managed.

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