fix: harden engine, enrich failure diagnostics, close adoption gaps

- P0: CLI verify now honors  test budget with seeded multi-sample
- P0: Observe sampling enforced via Math.random() gate in hook-validator
- P1: Remove misleading undici-mock-agent isolation option
- P1: Qualify reuses shared discoverRouteDetails() with warnings
- P1: Chaos/scenario config exposed via preset schema
- P1: README/docs limitations updated to current state
- P2: Nested response annotations prefer 2xx deterministically
- P2: --changed documented as heuristic in verify.md

- Add observe sink tests (sampling 0/1, sink failure non-interference)
- Add verify runs regression tests (scale, determinism, variants)
- Add configured-scenario qualify test (independent of OAuth fixture)
- Add coverageBreakdown to qualify artifacts (per-gate route coverage)
- Add production-style observe example with real sink in docs/observe.md
- Add nightly/staging vs PR gating guidance to docs/qualify.md

- Enrich VerifyFailure with formula-aware diagnostics:
  status:201 => 'HTTP 200', body field checks => actual values
- Remove stale observe CLI activation message
- Document outbound mocks as process-global in getting-started.md
- Refresh APOPHIS_ADOPTION_AUDIT.md with current state

903 tests pass, build clean, typecheck clean.

docs/attic/adoption-certification-scorecard.md

@@ -78,7 +78,7 @@ Rate each dimension from **1 (poor)** to **5 (excellent)**.
 
 | Dimension | Rating (1-5) | Evidence / Notes |
 |-----------|--------------|------------------|
-| Setup friction | 5 | `npm install apophis-fastify` + `npx apophis init` + `npx apophis verify` — three commands to first value. |
+| Setup friction | 5 | `npm install @apophis/fastify` + `npx apophis init` + `npx apophis verify` — three commands to first value. |
 | Time-to-first-value | 5 | Default `depth: 'quick'` runs in seconds. Immediate feedback on route contracts. |
 | CI confidence | 4 | `verify` in CI with `--format json-summary` gives pass/fail gate. Artifact retention allows post-hoc debugging. |
 | Replay reliability | 5 | `--replay` is single copy-paste command. Seed is printed in every failure. |
@@ -131,7 +131,7 @@ Attach the following to this scorecard:
 
 ### Setup (all personas)
 ```bash
-npm install apophis-fastify
+npm install @apophis/fastify
 npx apophis --help          # exits 0
 npx apophis init            # writes scaffold
 npx apophis doctor          # passes