chore(tooling): finalize Phase-1 extractor + drift-checker + scenario hygiene

- extract-fingerprint.ts: recover UA template and billing template from
  Bun-binary string dumps so 2.1.113+ extractions keep producing usable
  output even when the source is a native binary instead of cli.js.
- drift-checker/check-cch-constants.ts: npm-mode now delegates to
  extract-cc-bundle.ts so the 2.1.113+ Bun-native distribution is covered
  by `check:cch-drift:npm` rather than silently breaking.
- verification/generate-long-context-prompt.ts: deterministic prompt
  generator used by long-context scenarios; removes hand-maintained
  multi-KB prompts from scenario JSON.
- verification/scenarios/adaptive-thinking-shared.json: shorten prompt to
  avoid hitting local per-request timeouts during Sonnet captures (the
  previous wording could trigger a multi-second thinking chain that
  collided with the harness backoff window).
- tests/unit/analysis/extract-fingerprint.test.ts: regression coverage
  for the new Bun-binary template-literal fallback path.
- tests/integration/scripts/fingerprint-manifest-scripts.test.ts: pass
  --markdown-output for the bookkeeping-diff test so it no longer leaks a
  `2.1.108-to-2.1.108.md` artifact into the tracked tree on every run.
- manifests/reports/diffs/2.1.108-to-2.1.108.md: delete the polluted
  test byproduct (zero-content same-version diff).
- .gitignore: ignore `manifests/reports/diffs/*.json` (generated by the
  diff-manifests tool) and `.sandbox/` (Phase 2 dev-sandbox root).

Closes the post-Phase-1 tooling hygiene work; unblocks Phase 2 sandbox.