[rush reporter][R1B] Generate install-run-rush bootstrap protocol

[Sean Larkin (TheLarkInn)]

Summary

• make the reporter's self-contained bootstrap envelope encoder and protocol-major constant the source of truth for a generated rush-lib module
• run a deterministic Heft build check that fails when the reporter protocol sources and committed generated artifact diverge
• embed the generated local module in the existing install-run-rush webpack entry without importing @rushstack/rush-reporter at runtime

Stack

• parent: Wire rush-reporter package dependencies #5985 (copilot/reporter-r1a-package-wiring)

This is the R1B child of #5985. Auto-merge stays disabled while #5985 is open. After #5985 merges, retarget this PR to main, verify its slice and CI, then merge it before #5987.

Generation and boundary guarantees

libraries/reporter/scripts/generateBootstrapProtocol.js extracts only the marked zero-dependency protocol region, verifies its major matches REPORTER_PROTOCOL_VERSION.major, rejects imports/require() calls, and writes the committed artifact. Reporter builds execute the same renderer in check-only mode and compare the artifact deterministically after normalizing checkout line endings.

The generated module contains only the frozen major, envelope DTO types, and JSON.stringify encoder. The built install-run-rush.js contains the encoder and contains no @rushstack/rush-reporter reference.

Validation

• heft test --clean --test-path-pattern Bootstrap --max-workers 2 in libraries/reporter
• heft build --clean in libraries/rush-lib
• node libraries/reporter/scripts/generateBootstrapProtocol.js --check
• CRLF-safe stale-artifact generation check
• combined final-tip Rush build/tests, rush check, and rush change --verify --no-fetch
• gh pr diff 5986 contains only the 10-file R1B bootstrap-generation slice

Non-goals

This slice does not add reporter dependencies to rush-lib or apps/rush, change the PNPM lockfile, or implement the bootstrap handoff prelude. Those remain separate workstreams; this PR only establishes the generated protocol artifact and build guard.

Part of #5974

[Sean Larkin (TheLarkInn)]

Linear stack update: R1B is now head 1b4252c based on #5985. Its GitHub diff is exactly the 10-file bootstrap-generation slice; CRLF-safe generation and the committed generated protocol remain intact. Auto-merge is disabled until #5985 merges.

[Sean Larkin (TheLarkInn)]

Combined deep review of current head 1b4252ccd8.

No critical, high, or medium actionable findings. No useful low follow-ons.