* fix: replace broken bun:bundle shim with source pre-processing
The `onResolve`/`onLoad` plugin shim for `bun:bundle` was silently
ineffective in Bun v1.3.9+ — the `bun:` namespace is resolved by
Bun's native C++ resolver before the JS plugin phase runs. This meant
ALL `feature()` flags evaluated to `false` regardless of the
`featureFlags` map in build.ts (including `MONITOR_TOOL: true`).
Replace the shim with a source pre-processing step that:
1. Strips `import { feature } from 'bun:bundle'` from .ts/.tsx files
2. Replaces `feature('FLAG')` calls with boolean literals
3. Restores original files in a `finally` block after Bun.build()
Also extend the missing-module scanner to detect `require()` and
dynamic `import()` calls — not just static `import ... from` — since
modules behind feature() gates become resolvable when flags are enabled.
* fix: ensure source files are always restored after build
- Add SIGINT/SIGTERM handlers to restore pre-processed source files
on abrupt termination (Ctrl+C, kill)
- Replace process.exit(1) with process.exitCode = 1 so the finally
block runs on build failure
adbe391e63