fix(security): close remaining /bin/sh -c shell-injection sites in bundle ID flows

[voidborne-d]

Follow-up to #289 that closes the four shell-injection sites called out in #367.

Problem

PR #289 routed the useShell=true path of defaultExecutor through shellEscapeArg. That fix does not cover call sites that build their own /bin/sh -c command strings and hand them to the executor with useShell=false as ['/bin/sh', '-c', command]. Those sites interpolate user-controlled paths into the shell string and are vulnerable to CWE-78.

Four sites are flagged in #367 and confirmed on main:

• src/utils/bundle-id.ts — defaults read \"${appPath}/Info\" CFBundleIdentifier and the PlistBuddy fallback
• src/mcp/tools/project-discovery/get_mac_bundle_id.ts — same pattern, Contents/Info plist
• src/mcp/tools/macos/build_macos.ts — same pattern in the post-build bundle-ID extraction
• src/utils/macos-steps.ts — same pattern after open (used by launch_mac_app and build_run_macos)

The accompanying UNFIXED: regression tests in bundle-id-injection.test.ts and mac-bundle-id-injection.test.ts documented the live attack vectors (\$(id), ; rm -rf /, backticks).

Fix

Each site now invokes defaults or PlistBuddy directly with an argv array, picking option (1) from the issue ("stop using /bin/sh -c") rather than option (2) (shellEscapeArg-everywhere). Removing shell parsing entirely is the smaller, safer surface — there is nothing left to escape, and we do not need to keep a useShell plumbing path alive for these helpers.

```ts
// before
await executor(
['/bin/sh', '-c', `defaults read "${appPath}/Info" CFBundleIdentifier`],
'Bundle ID Extraction',
);

// after
await executor(
['defaults', 'read', `${appPath}/Info`, 'CFBundleIdentifier'],
'Bundle ID Extraction',
false,
);
```

defaults and /usr/libexec/PlistBuddy accept paths and key arguments positionally, so no shell features are needed. A malicious appPath becomes a single literal argv element and is never seen by a shell parser.

Tests

• The 4 UNFIXED: regression cases are flipped to safe assertions: command does not start with /bin/sh, useShell is false, the argv array matches the expected defaults / PlistBuddy shape exactly.
• New PlistBuddy-fallback cases in both injection suites assert the same shape on the fallback branch (when defaults returns failure).
• Existing mock-command fixtures in get_app_bundle_id.test.ts, get_mac_bundle_id.test.ts, and build_run_device.test.ts updated to the new argv-shape command keys (the createCommandMatchingMockExecutor matches on command.join(' '), so the old double-quoted strings no longer match the new argv form).

Pre-fix verification

```
$ git stash push -- src/utils/bundle-id.ts \
src/mcp/tools/project-discovery/get_mac_bundle_id.ts \
src/mcp/tools/macos/build_macos.ts \
src/utils/macos-steps.ts
$ npx vitest run src/utils/tests/bundle-id-injection.test.ts \
src/utils/tests/mac-bundle-id-injection.test.ts
... 8 failed (8) ...
$ git stash pop
$ npx vitest run src/utils/tests/bundle-id-injection.test.ts \
src/utils/tests/mac-bundle-id-injection.test.ts
... 8 passed (8) ...
```

Local gates

• `npm run typecheck` — clean (`npx tsc --noEmit && npx tsc -p tsconfig.test.json`)
• `npm run lint` — clean
• `npm run format:check` — clean
• `npm test` — 1772 passed / 0 failed across 167 files (no other tests touched bundle-id command shape)

Notes

• This PR does not modify defaultExecutor itself; the existing useShell=true hardening in fix: CWE-78 shell injection via unsafe argument escaping in command executor #289 stays as-is for the call sites that genuinely need it.
• CHANGELOG entry added under `[Unreleased] / Fixed`.
• AI assistance disclosure: I used Claude (Opus 4.7) while drafting and verifying this change. All edits, regression-test pre/post-fix verification, and local gate runs were reviewed by me before commit.

Closes #367

[pkg-pr-new]

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npm i https://pkg.pr.new/xcodebuildmcp@390

commit: 852f1b0