fix: handle Windows multiscan path aliases

[faizan-oai]

Summary

Severity: P1–P2. Creating a new campaign below a Windows junction can fail before multiscan reaches the scanner, and equivalent repository aliases can prevent a campaign from resuming. This canonicalizes the stable filesystem portions used for creation and comparison.

Changes

• Resolve the nearest existing campaign ancestor before recursive directory creation on Windows.
• Canonicalize existing local repository paths before multiscan records or compares them.
• Preserve the validated canonical campaign directory for subsequent operations.
• Add Windows junction and repository-alias regressions.

Testing

• pnpm run format — passed.
• pnpm run types — passed.
• pnpm run build — passed.
• Focused Windows multiscan alias regressions — 2 passed.
• git diff --check origin/main...HEAD — passed.

Risk and rollout

User-selected parent junctions remain supported, while linked output directories and post-validation redirection protections remain unchanged. Canonicalization applies only to existing local paths. No migration is required.

Public disclosure review

• No customer, partner, prospect, or user identities, data, or identifying details are included.
• No credentials, personal data, private source, scan findings, or nonpublic links or tickets are included.
• I reviewed the branch name, title, description, commits, changes, comments, logs, screenshots, attachments, and links for public disclosure.

[mldangelo-oai]

Reviewed e1a84b4a190f for correctness and simplification. One optional consolidation with the related portable-path PR.

This is a non-blocking review. I did not run the full SDK suite or native Windows tests locally.

[mldangelo-oai]

Rechecked e1a84b4. The earlier simplification suggestions remain non-blocking. Approving the reviewed head.