fix(verify): disclose skipped cross-checks and report URL schemes per platform

[mohn93]

Problem

Reported by a developer integrating flutter_ulink_sdk (domain abrezo.shared.ly) who saw ulink verify (v1.3.1) print a green PASS on a project whose deep-link setup had never actually been cross-checked.

Two distinct issues, both confirmed against the code:

1. Silent green PASS. The AASA / assetlinks / dashboard cross-checks were not removed in v1.3.1 — they are gated on a successful authenticated project-config fetch. On an unauthenticated run (or a project selected without credentials) they are skipped, but the default report never counted or displayed skipped checks, so it printed a bare ✓ PASSED. A green run was therefore compatible with deep linking being completely unverified.

2. URL schemes pooled across platforms. For a Flutter project the parser keeps correct per-platform lists but also builds a combined urlSchemes union. IosValidator and AndroidValidator printed that union under both platform headers, so verify -v showed an iOS-only scheme under Android and vice versa. (The actual scheme matching was already per-platform-correct — this was display only.)

Changes

• VerificationReport: add skippedCount / hasSkipped.
• verify: emit an explicit skip result whenever the dashboard cross-check does not run — now including the project-selected-but-no-credentials case, which previously produced no notice at all.
• Default report: show the skipped count, a NOT VERIFIED section (what was not checked and why), and a qualified PARTIAL status. A clean ✓ PASSED is now reserved for a run with zero skips. Verbose report and JSON summary made consistent.
• IosValidator / AndroidValidator: read iosUrlSchemes / androidUrlSchemes instead of the pooled urlSchemes.
• Tests: guards against cross-platform scheme pooling and against a silent green PASS.

Behaviour (bare ulink verify, unauthenticated, real Flutter project)

flutter | ✓ 9 passed  ⊘ 1 skipped

⊘ NOT VERIFIED:
  Dashboard cross-check (bundle id, team id, package, fingerprints, AASA & assetlinks.json)
    No credentials — local files were NOT compared against the ULink dashboard
    config, and the hosted well-known files were not fetched.
    → Run "ulink login" ... Without this, verify only confirms local files exist —
      not that deep linking actually resolves.

⚠ PARTIAL - local checks passed, but 1 check was skipped. This is NOT a full verification.

Not addressed here (follow-ups)

• pbxproj target selection. IosParser._extractVariableFromPbxproj still resolves PRODUCT_BUNDLE_IDENTIFIER globally ("first non-Test match in file order"), so in a multi-target project (app + extensions + tests) it can still resolve to an extension's id. Needs a target-scoped resolver; tracked separately.
• Exit code. PARTIAL still exits 0 (incomplete, not failed) to avoid breaking curl … | ulink verify smoke tests and unauthenticated CI. A --strict flag to exit non-zero on skips can be a separate change.

Testing

dart analyze lib test clean. dart test — 296 pass (4 new guards).