Collect React Compiler coverage stats and triage actionable vs unsupported-syntax errors

> **Performance audit finding** · Severity: **Medium** · Effort: Medium · Fix risk: Simple (build-time only) · Test safety net: N/A (tooling)
> Owner: `@MetaMask/mobile-platform (suggested)`
> File: `babel.config.js:67`

### What is this about?

React Compiler is fully enabled (#31171) via the bare `'react-compiler'` Babel plugin — **with no `logger`, no error categorization, and no coverage accounting**. The compiler fails open: any component it can't compile is silently skipped and ships unoptimized (#30919 counted 53 class components in that bucket at enablement). Today there is no way to answer "what is the compiler actually compiling, and which of its errors are worth fixing?" without ad-hoc spelunking.

The critical triage split the logger enables: on `CompileError`, `event.detail.options.category === 'Todo'` means **unsupported syntax** (an unimplemented compiler feature — no actionable fix on our side), while any other category (`InvalidReact`, `InvalidJS`) is a **legitimate, actionable Rules-of-React violation**. Without this split, the Todo noise drowns the actionable list. (Category names verified against `babel-plugin-react-compiler@1.0.0`.)

**Example — the extension's verbose run at enablement (metamask-extension#38007):**

| Status | Files |
|---|---:|
| ✅ Compiled | 253 |
| ⏭️ Skipped | 0 |
| ❌ Errors (actionable) | **31** |
| 🔍 Unsupported (`Todo`) | 7,024 |
| 📦 Total processed | 7,308 |

Read without the split, this is ~7,000 hopeless "errors". Read with it, the actionable backlog is **31 files** — a tractable list — while the 7,024 `Todo`s are the compiler's backlog to burn down across upgrades, re-diffed per version bump. That is the entire value proposition of the categorized logger.

### Scenario

N/A — build tooling.

### Design

N/A.

### Technical Details

**Fix**

Pass a `logger` in the Babel plugin options that buckets events into compiled / skipped / error / unsupported (worst-status-wins per file) and prints a summary, gated behind an env flag for opt-in verbose builds. Reference implementation: the extension's webpack integration (metamask-extension#38007, `--reactCompilerVerbose` / `--reactCompilerDebug={all|critical|none}` mapping to `panicThreshold`). The ratchet end-state: a non-production build that passes `panicThreshold: 'critical_errors'`, then `'all_errors'` (production stays `'none'` permanently).

### Threat Modeling Framework

N/A — build-time tooling; no runtime change.

### Acceptance Criteria

- An env-gated build prints compiled/skipped/error/unsupported counts (file and component granularity) with `'Todo'`-category errors bucketed as unsupported.
- The actionable-error list (non-`Todo`) is tracked and trends down; the unsupported list is re-diffed on compiler upgrades.

### References

- Files: `babel.config.js:67`
- Dependent: #31507 (the `panicThreshold` ratchet burns down the actionable-error list this logger produces)
- Reference implementation: metamask-extension#38007 (`reactCompilerLoaderWrapper.ts`, `ReactCompilerPlugin`)
- Source: `mms-performance` skill, `mm-react-compiler-error-triage` (MetaMask/skills#49)
- Status: tooling proposal

Start at babel.config.js:67 and inspect how the react-compiler plugin is configured, then compare the reference integration in reactCompilerLoaderWrapper.ts and ReactCompilerPlugin. Run a non-production build with the proposed environment flag and verify compiled, skipped, actionable-error, and Todo/unsupported counts at file and component granularity.

Written by the indexing model from the issue text.