Fix banner tap routing and session restore crash

[SoundBlaster]

Summary

• Banner tap did nothing: Tapping "View Integrity Report" now opens the integrity inspector panel and dismisses the banner. Previously the onTap handler only called focusIntegrityDiagnostics() which selected a node internally but never set showInspector = true, so nothing was visible to the user.
• Startup crash on duplicate session URLs: SessionPersistenceService.applySessionSnapshot used Dictionary(uniqueKeysWithValues:) which fatally crashes when two session file entries share the same canonical URL. Switched to Dictionary(_:uniquingKeysWith:) keeping the entry with the lower orderIndex.

Test plan

• Open a file with integrity issues — banner appears with "View Integrity Report"
• Tap "View Integrity Report" — inspector panel opens, banner dismisses
• Relaunch app with a session snapshot that contains duplicate file URLs — no crash
• All 382 existing tests pass

🤖 Generated with Claude Code

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[github-actions]

🔍 SwiftLint Code Quality Report

✅ No violations found! Code quality check passed.

[github-actions]

📊 Coverage Gate Results

SUMMARY
================================================================================

Total Source LOC: 5,578
Total Test LOC:   4,962
Overall Test/Code Ratio: 89.0%

Layer                  Source LOC     Test LOC      Ratio
------------------------------------------------------------
Layer 0                        96          142     147.9%
Layer 1                       779          617      79.2%
Layer 2                     1,048          794      75.8%
Layer 3                     2,175        1,448      66.6%
Layer 4                       834        1,442     172.9%
Utilities                     646          519      80.3%

Threshold: 67%
Coverage: 89.0%
Status: ✅ PASS