refactor(v8-bridge): modularize the bridge into a per-subsystem TypeScript package

[NathanFlurry]

Follow-up to #164. Finishes turning the V8 bridge into a clean multi-file TypeScript package and removes the generated intermediate.

• Remove the committed crates/execution/assets/v8-bridge.source.js seam: build-v8-bridge.mjs now generates the readable bundle in memory from bridge-src/index.ts and minifies it directly, so there is no generated .source.js to keep in sync.
• Repoint the tools that read the old seam text at the TypeScript sources directly (polyfill-registry check, browser util-polyfill codegen, limits inventory audit, bridge rerun inputs).
• Split the two mega-modules into per-subsystem files: network.ts into net/http/http2/dns/tls/dgram/fetch/sqlite, and process.ts into process/console/stdin/timers/crypto/vm/v8/perf/misc-stubs.
• Split polyfills.ts into text-encoding/dom-events/abort/web-streams-fallback, extract the misfiled Undici client out of child-process.ts into its own module, and split the builtin-module registry out of module-loader.ts.
• Preserve the sidecar/js/executor interface: no changes to the bridge contract, installed globals, module surface, or dispatch behavior.
• Fix module-cycle initialization order issues introduced by the split (tty stubs and the sqlite/net/tls/dgram module-global installs), and add guest-runtime regression tests for require('tty') and require('sqlite').
• Remove vestigial provenance comments and a dead import left over from the original bundle.
• Unblock the workspace build by fixing pre-existing breakage unrelated to the bridge: the browser wire dispatcher now handles the LinkPackage route, its ConfigureVmRequest test constructors set the newer fields, and the build-tools type check drops a dangling script reference.