Resolve IntegrationTests-025: stopBoundary for repo-root walker

ResolveRepositoryRoot accepts an optional stopBoundary parameter that
caps the upward walk; production callers pass null and behavior is
unchanged. The two repository-marker tests now seal their walkers
inside their own temp directories, so a redirected TMP or a co-located
C:\src checkout no longer leaks ambient marker-bearing ancestors into
the assertion.

Regression test ResolveRepositoryRoot_StopBoundary_IsolatesWalkerFromAmbientAncestorMarkers
constructs an outer ancestor that carries src/ + .git, confirms the
walker leaks into it without the boundary, then asserts the same call
throws with the boundary supplied.

Resolved at 2026-05-24; IntegrationTestEnvironmentTests 5/5 pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

code-reviews/IntegrationTests/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-24 |
 | Commit reviewed | `42b0037` |
 | Status | Re-reviewed |
-| Open findings | 1 |
+| Open findings | 0 |
 
 ## Checklist coverage
 
@@ -494,7 +494,7 @@ The Write parity test (IntegrationTests-012's resolution) added exactly this ass
 | Severity | Low |
 | Category | Correctness & logic bugs |
 | Location | `src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironmentTests.cs:57-84` (`ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The new regression test for IntegrationTests-022 builds an "isolated" start directory under `Path.GetTempPath()` (e.g. `C:\Users\<user>\AppData\Local\Temp\<random>\nested` on Windows) and calls `ResolveRepositoryRoot(isolatedStart)`, asserting an `InvalidOperationException` is thrown. The walker walks every parent — `<random>`, `Temp`, `Local`, `AppData`, `<user>`, `Users`, `C:\` — and stops only when it either finds a repository root marker or runs out of parents. The test silently assumes none of those ancestor directories satisfies `IsRepositoryRoot` (a `src/` subdirectory next to `.git` / `*.sln` / `*.slnx`). The assumption is environment-dependent:
 
@@ -504,3 +504,5 @@ The Write parity test (IntegrationTests-012's resolution) added exactly this ass
 The current dev box layout (`C:\Users\dohertj2\Desktop\mxaccessgw`) is safe because Temp is at `C:\Users\dohertj2\AppData\Local\Temp` and the walker exits at `C:\` without ever encountering `src/`. The fragility is invisible on this machine and only surfaces if the test ever runs in CI / on a contributor box with a less hermetic file-system layout.
 
 **Recommendation:** Isolate the walker from any ambient ancestor by either (a) constructing an `isolatedRoot` directly under a drive root and pointing the walker at a chain entirely under it (e.g. create `<isolatedRoot>\level1\level2\level3` and start the walk at `level3`, then assert the throw — the walker stops at the drive root regardless of what is on it), (b) refactoring `ResolveRepositoryRoot` to accept an injectable `stopBoundary` parameter for tests and pass `isolatedRoot` as the boundary, or (c) replacing the `Assert.Throws` shape with an explicit upward-walk check that the test owns. Option (a) is the smallest change: prepend a sentinel — e.g. create a dummy `<isolatedRoot>\sentinel-no-markers` and assert nothing about Temp ancestors — and pass the test only when the walker reaches that sentinel without finding a marker. The current shape is acceptable on the documented dev box but should not be the sole regression coverage for IntegrationTests-022.
+
+**Resolution:** Resolved 2026-05-24 — Took option (b) (inject a stop-boundary) because option (a) does not actually solve the leak: a sentinel chain under `Path.GetTempPath()` still leaves the walker free to ascend past it into Temp / AppData / Users / C:\, so any ambient ancestor with `src/` + `.git`/`.sln`/`.slnx` still wins. Added an optional `stopBoundary` parameter to `IntegrationTestEnvironment.ResolveRepositoryRoot(string startDirectory, string? stopBoundary = null)`. When supplied, the walker checks the boundary for markers and then stops, refusing to ascend past it; production callers (the `MXGATEWAY_LIVE_MXACCESS_WORKER_EXE` resolution path) continue to pass `null` so the walk to drive-root behavior is unchanged. Updated both existing tests (`ResolveRepositoryRoot_AcceptsGitWorktreeFile` and `ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) to pass their owned temp directory as the boundary, sealing the walker inside a chain the test fully controls. Added a new regression test `ResolveRepositoryRoot_StopBoundary_IsolatesWalkerFromAmbientAncestorMarkers` that deliberately constructs an outer marker-bearing ancestor (`outerRoot/src` + `outerRoot/.git`), an inner boundary, and an isolated start beneath the boundary; first asserts that without the boundary the walker leaks up to `outerRoot` (the precise IntegrationTests-025 failure mode), then asserts that *with* the boundary the same call throws — proving the boundary is the load-bearing isolation. TDD red/green confirmed: the new regression test fails against the pre-fix walker (`Assert.Throws() Failure: No exception was thrown`) and passes once the boundary handling is restored. Re-ran the full `IntegrationTestEnvironmentTests` slice with `TMP` / `TEMP` redirected under a deliberately constructed `<temp>\fake-repo-ancestor` directory carrying `src/` and a `.git` file — the original flake repro from the finding — and confirmed all 5 tests pass (the same redirection produced `Assert.Throws() Failure` on the pre-fix code). Build: 0 warnings / 0 errors.