Re-enable 18 quarantined AgentHubCore tests (headless failures + hangs)

[jamesrochabrun]

Summary

The AgentHubCore test suite now runs headlessly (./scripts/test.sh, and CI via .github/workflows/test.yml). The first time it ran outside Xcode's Cmd+U it surfaced 18 tests that fail or hang headlessly. To keep the gate green they are temporarily quarantined with .disabled("headless-quarantine: …") and documented in TestQuarantine.md.

None of these are fixed — each is a real bug or a flaky/non-deterministic test. This issue tracks fixing the root causes and removing the .disabled(...) traits. They group into 4 root causes; A is a genuine product concurrency bug and the highest priority.

To work one: remove its .disabled(...) trait and run
cd app/modules/AgentHubCore && xcodebuild test -scheme AgentHubCore-Tests -destination 'platform=macOS' -test-timeouts-enabled YES -only-testing:<Target>/<SuiteType>/<method>.

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A — Git subprocess deadlock on non-git paths (product bug · HANG) 🔴

GitDiffService.runGitCommand (AgentHubGitDiff/Services/GitDiffService.swift) spawns /usr/bin/git and reads its pipes with Pipe() + readToEnd() + readGroup.wait(). Under concurrent spawning (parallel tests, and the real app), pipe write-end FDs are inherited by sibling git children, so readToEnd() never sees EOF until those unrelated children exit — the call blocks until the 30s gitCommandTimeout fires. Raw git rev-parse --show-toplevel on a non-git dir returns in 0.00s, so this is purely the Swift Process/pipe handling, not git. This likely causes real app responsiveness issues, not just test hangs.

Fix direction: set close-on-exec on the pipe FDs (or use posix_spawn_file_actions); and/or fast-fail findGitRoot when libgit2 has already reported "no repository" instead of falling back to the CLI.

• DiffAvailabilityServiceTests → "Non-git path is unavailable"

B — Reactive / async-delivery timing (test fragility, product-adjacent)

These poll waitUntil { … } / await condition() for state delivered via Combine .values async sequences or real Date.now/sleep-based throttles. Values sent between awaits get dropped, or the timing window is too tight under headless parallel load. The CLISessionsViewModel subscription is setupSubscriptions() (CLISessionsViewModel.swift, for await … repositoriesPublisher.values).

Fix direction: make delivery deterministic (await the publisher directly / inject a clock / pump the run loop) instead of wall-clock polling.

• FocusedSessionLaunchTargetResolverTests → "Preselect accepts a path inside a tracked worktree"
• FocusedSessionLaunchTargetResolverTests → "Preselect accepts a path inside a tracked main repository"
• LazyBrowseSessionsLoadingTests → "Idle repository changes still trigger Claude hook sync"
• WebPreviewInspectorViewModelTests → "Toolbar text edits do not mutate live preview without source text mapping"
• WorktreeBranchNamingServiceTests → "Explicit user cancellation stops naming without falling back" (also slow/hang)
• GitWorktreeServiceTests → "Cancels in-flight worktree creation and cleans up generated artifacts"
• DiffAvailabilityServiceTests → "Fast evaluator keeps the minimum floor" (Fix CPU burn: adaptive diff-refresh throttle + zero-XPC simulator capture #379 throttle)
• GitDiffServiceTests → "fast evaluator keeps the minimum floor" (Fix CPU burn: adaptive diff-refresh throttle + zero-XPC simulator capture #379 throttle)
• GitDiffServiceTests → "invalidate succeeds after the adaptive window elapses" (Fix CPU burn: adaptive diff-refresh throttle + zero-XPC simulator capture #379 throttle)

C — Temp-dir symlink path normalization

macOS temp dirs (/var/folders/…, /tmp) are symlinks to /private/…. Fixtures pass the unresolved path; some product comparisons resolve symlinks and some don't, so prefix/equality checks mismatch. WorktreeModuleResolver.normalizedDirectoryPath and CLISessionsViewModel.isProjectPath do raw prefix matching without resolvingSymlinksInPath().

Fix direction: resolve symlinks consistently (canonicalize in the product path helpers, or resolve fixture temp paths). Decide whether product code should canonicalize.

• GitDiffServiceTests → "branch changes are scoped to the selected worktree"
• SpotlightProjectFileSearchServiceTests → "Ranks Spotlight paths and filters directories and paths outside the project"
• WorktreeSettingsInventoryTests → "Delete worktree for nested session removes the worktree root" (may overlap with B)

D — Deterministic product-vs-test drift / latent bugs (decide which side is right)

• CodexTimestampParserTests → "Returns nil for invalid timestamps" — product bug: the strict byte-parser rejects 2026-02-31, but the ISO8601DateFormatter fallback (CodexTimestampParser.swift) leniently rolls it to Mar 3. Reject in the fallback, or relax the test.
• EmbeddedTerminalLaunchBuilderTests → "Claude launch passes raw prompt, AgentHub MCP config, and installs worktree skill" — asserts shellCommand.contains("/bin/sh") but the MCP-config JSON escapes slashes as \/bin\/sh. Test too literal, or builder should encode with .withoutEscapingSlashes.
• EmbeddedTerminalLaunchBuilderTests → "Blank Claude launch still passes AgentHub MCP config and installs worktree skill" — same JSON slash-escaping issue.
• InlineEditStyleReconcilerTests → "Forwards request fields to the programmatic service" — system prompt no longer contains "preserve the semantic change"; prompt text drifted vs the test.
• SpotlightProjectFileSearchServiceTests → "Escapes quoted query literals before building the metadata query" — the backslash-escape branch in SpotlightQueryBuilder.escapeQuotedString appears unreachable because \ is consumed as a path separator by filename-component extraction first.

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Context: headless test infrastructure added in this branch (scripts/test.sh, AgentHubCore-Tests scheme, CI test.yml). Full root-cause notes live in TestQuarantine.md.