docs: Add targeted snapshot test guidance

[cameroncooke]

Add contributor docs for targeted snapshot test workflows.

The testing guide already covered full snapshot runs and fixture regeneration, but it did not explain how to add a new snapshot test case, how fixture scenario names map to fixture paths, or how to run and update a single targeted snapshot test. This adds those practical examples so contributors can iterate without running the full snapshot suite every time.

The examples focus on the device suite because it is a common source of environment-sensitive fixture updates.

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Project	Deployment	Actions	Updated (UTC)
xcodebuildmcp-com	Ready	Preview, Comment	Apr 28, 2026 3:14pm

[sentry]

Bug: The documented Vitest filter command -t "list success" may not work if tests are nested, as Vitest uses > as a separator, not a space.
_{Severity: MEDIUM}

Suggested Fix

Verify the actual test suite structure in the getsentry/XcodeBuildMCP repository. If tests are nested, update the command in the documentation to use the correct separator, for example: -t "list > success". Alternatively, clarify the documentation by showing the exact describe/it structure that results in the documented command working correctly.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: app/docs/_content/testing.mdx#L147

Potential issue: The documentation for running snapshot tests provides a Vitest filter
command, `-t "list success"`, to run a specific test. However, Vitest's official
documentation specifies that nested `describe` and `it` blocks are separated by a `>`
character in the full test name (e.g., `"list > success"`). The provided command uses a
space, which would only work if the test name was flat, like `it('list success', ...)`.
Because the actual test suite structure is not shown and nesting is a common pattern,
the documented command is likely to silently fail by matching zero tests, causing
confusion for contributors trying to use this feature.

_{Did we get this right? 👍 / 👎 to inform future reviews.}