Fix inventory duplication, cleanup JSON, and PTY quit handling

[harder]

Summary

• Resolve existing Unix path aliases when merging gh skill list with the filesystem scan, and reuse the case-sensitivity result per parent directory. This removes duplicate /var versus /private/var installs on macOS and avoids repeated directory probing.
• Keep --json independent of a bare cleanup --candidates option.
• Accept Ctrl+Alt+Q as quit when the ANSI driver combines bare Escape followed by Ctrl+Q. Extend the opt-in PTY test to cover this sequence, add rapid tab-switching coverage, and document the headless PTY behavior.

Verification

• dotnet build --no-restore — clean
• dotnet test --no-build — 828 passed
• Opt-in PTY startup/quit test — passed; three additional headless Escape → Ctrl+Q runs exited cleanly
• Live gh contract tests — 6 passed
• dotnet format SkillView.sln --no-restore --verify-no-changes — passed
• macOS arm64 Native AOT publishes for both entrypoints — passed
• Isolated CLI walkthrough: list, remove preview, cleanup JSON, remove apply, and broken-link cleanup — passed
• Synthetic inventory of 1,500 skills: list now returns 1,500 records in about 1.4 seconds, versus 3,001 records and 25 seconds or a timeout before the fix

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused fixes are consistent with repository conventions and include appropriate regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes inventory alias duplication, cleanup argument parsing, and PTY quit handling.

Changes:

• Canonicalizes Unix paths and caches case-sensitivity probes during inventory merging.
• Prevents bare --candidates from consuming --json.
• Supports Ctrl+Alt+Q and expands TUI/PT​​Y regression coverage.

File	Description
src/​SkillView.Core/​Inventory/​LocalInventoryService.cs	Resolves path aliases during merges.
src/​SkillView.Core/​Cli/​CliDispatcher.cs	Corrects cleanup option parsing.
src/​SkillView.Core/​Ui/​SkillViewApp.cs	Accepts Alt-modified Ctrl+Q.
tests/​SkillView.Tests/​Inventory/​LocalInventoryServiceMergeTests.cs	Tests Unix alias deduplication.
tests/​SkillView.Tests/​Cli/​CliDispatcherParserTests.cs	Tests bare candidate parsing.
tests/​SkillView.Tests/​Ui/​SkillViewAppTests.cs	Tests Ctrl+Alt+Q detection.
tests/​SkillView.Tests/​Ui/​PtyStartupTests.cs	Exercises PTY Escape/Ctrl+Q shutdown.
tests/​SkillView.IntegrationTests/​Ui/​SkillViewAppIntegrationTests.cs	Covers rapid tab switching.
AGENTS.md	Records the PTY quit invariant.
agent_docs/​tui-pty-testing.md	Documents headless PTY behavior.

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