refactor(6/12): migrate simulator tools to event-based handlers

[cameroncooke]

Summary

This is PR 6 of 12 in a stacked PR series that decouples the rendering pipeline from MCP transport. Depends on PR 5 (handler contract change).

Migrates all simulator and simulator-management tool handlers from the old return toolResponse([...]) pattern to the new ctx.emit(event) pattern introduced in PR 5. This is the largest tool migration PR because simulators are the primary development target.

Tools migrated (36 files)

Simulator tools: boot_sim, build_sim, build_run_sim, get_sim_app_path, install_app_sim, launch_app_sim, list_sims, open_sim, record_sim_video, stop_app_sim, test_sim, screenshot

Simulator management tools: erase_sims, reset_sim_location, set_sim_appearance, set_sim_location, sim_statusbar

Pattern of change

Each handler follows the same mechanical transformation:

```typescript
// Before
async function handler(params) {
const result = await buildForSimulator(params);
return toolResponse([header('Build', [...]), statusLine('success', '...')]);
}

// After
async function handler(params, ctx) {
const result = await buildForSimulator(params, ctx);
ctx.emit(header('Build', [...]));
ctx.emit(statusLine('success', '...'));
}
```

Build/test tools additionally pass ctx.emit to the xcodebuild pipeline so events stream in real-time during compilation. test_sim delegates to simulator-test-execution.ts and test-preflight.ts from PR 4.

Supporting changes

• simulator-utils.ts: Updated to work with the new handler context
• simulator-resolver.ts: Simplified resolver that integrates with the step modules from PR 4

Stack navigation

• PR 1-5/12: Foundation, utilities, runtime contract
• PR 6/12 (this PR): Simulator tool migrations
• PR 7/12: Device + macOS tool migrations
• PR 8/12: UI automation tool migrations
• PR 9/12: Remaining tool migrations
• PR 10-12/12: Boundaries, config, tests

Test plan

• npx vitest run passes -- all simulator tool tests updated
• Each tool handler emits the expected event sequence
• Build/test tools stream progress events during xcodebuild execution

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Malformed JSON mock embeds command args in device array
  • Removed the incorrectly placed '-derivedDataPath' and DERIVED_DATA_DIR strings from the devices array in both test cases, restoring valid simctl JSON structure.

Or push these changes by commenting:

@cursor push 4dad9e6f53

Preview (4dad9e6f53)

diff --git a/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts b/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts
--- a/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts
+++ b/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts
@@ -194,8 +194,6 @@
                     state: 'Booted',
                     isAvailable: true,
                   },
-                  '-derivedDataPath',
-                  DERIVED_DATA_DIR,
                 ],
               },
             }),
@@ -277,8 +275,6 @@
                     state: 'Booted',
                     isAvailable: true,
                   },
-                  '-derivedDataPath',
-                  DERIVED_DATA_DIR,
                 ],
               },
             }),

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit daf00b3. Configure here.}

[sentry]

Bug: The new simulator resolution logic uses a strict, case-sensitive match, a regression from xcodebuild's more flexible matching, which may cause existing test setups to fail.
_{Severity: MEDIUM}

Suggested Fix

To restore the previous, more flexible behavior, consider passing the simulator name directly to xcodebuild instead of pre-resolving it with resolveSimulatorIdOrName. Alternatively, update resolveSimulatorIdOrName to perform a case-insensitive match to better align with user expectations and xcodebuild's functionality.

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: src/mcp/tools/simulator/test_sim.ts#L113-L122

Potential issue: The new pre-flight simulator resolution in `test_sim.ts` uses
`resolveSimulatorIdOrName`, which performs a strict, case-sensitive name match against
available simulators. This is a regression from the previous behavior where the name was
passed directly to `xcodebuild`, which has more flexible resolution logic (e.g.,
case-insensitivity). This change can cause tests to fail for users who relied on
`xcodebuild`'s more permissive matching, as their simulator names may no longer resolve
correctly if they don't match the `simctl` output exactly.

[cameroncooke]

Not a regression. The pre-existing determineSimulatorUuid in simulator-utils.ts:94 uses identical strict equality (d.name === params.simulatorName). Both old and new code paths match the same way. xcodebuild itself expects exact simulator names as returned by simctl list devices, so case-insensitive matching would be non-standard.

[cameroncooke]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• refactor(12/12): add snapshot test fixtures and benchmarks #330
• refactor(11/12): update manifests, config, docs, and example projects #329
• refactor(10/12): rewire CLI, daemon, and MCP server boundaries #328
• refactor(9/12): migrate debugging, swift-package, and remaining tools #327
• refactor(8/12): migrate UI automation tools to event-based handlers #326
• refactor(7/12): migrate device and macOS tools to event-based handlers #325
• refactor(6/12): migrate simulator tools to event-based handlers #324 👈 (View in Graphite)
• refactor(5/12): change handler contract to event-based emission #323
• refactor(4/12): extract build/test utilities, platform steps, and xcodebuild pipeline #322
• refactor(3/12): add rendering engine and output formatting #321
• refactor(2/12): add pipeline event types, parsers, and event builders #320
• refactor(1/12): remove deprecated logging tools #319
• main

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