feat: wire --analyzer to gaze quality for external test_mapping (GazeCRAP + contract coverage)

[yvonnedevlinrh]

Background

gaze quality --analyzer was scoped in #95 alongside analyze, crap, and report.
Phase 2 (#178) delivered crap and report but explicitly deferred quality:
the --analyzer / --language flags are registered in cmd/gaze/main.go but
hidden from help and return an error if passed.

With #237 (callAndUnmarshal helper in internal/adapter/) and #238 (safeSSABuild
consolidated in internal/ssaguard/) now merged, the infrastructure blockers are gone.
The protocol is also complete: test_mapping is fully specified in protocol v1.1.0
(response schema, capability handshake, GazeCRAP integration, graceful degradation).
There is no longer a research/feasibility question — this is an implementation issue.

What's missing

Gaze side (this issue)

1. Unhide --analyzer and --language in cmd/gaze/quality.go
2. After detecting external-analyzer capability via initialize, wire the adapter to call
   test_mapping using the new callAndUnmarshal helper from refactor: extract generic callAndUnmarshal helper in internal/adapter/ #237
3. Feed the returned {mappings:[...]} into the GazeCRAP scoring path in place of the
   Go SSA test-pairing output
4. Fix the inaccuracy in website#227 / website#165 (these pages list quality as
   supporting --analyzer, which has never been true)

Snake-eyes side (separate issue)

Snake-eyes declares test_mapping: false in initialize and returns -32601 for
the method. Implementing pytest assertion → target-function → side-effect mapping
is scoped as a separate snake-eyes issue.

Acceptance criteria

• gaze quality --analyzer snake-eyes --language python -- ./... runs against a Python
  project and produces a quality report (or a clear graceful-degradation message when
  test_mapping is unavailable)
• When test_mapping is available (future snake-eyes issue), GazeCRAP scores are
  equivalent in structure to Go-based GazeCRAP scores
• The --analyzer flag appears in gaze quality --help
• CI green on existing Go quality tests (no regression)

References

• feat: external analyzer protocol (JSON-RPC over stdin/stdout) for multi-language support #95 — external analyzer protocol spec (closed)
• feat: extract provider interfaces for multi-language support (Phase 1 of #95) #165 — phase 1 quality refactor
• feat: JSON-RPC external analyzer protocol for multi-language support (Phase 2 of #95) #178 — phase 2 (crap/report delivered; quality deferred)
• refactor: extract generic callAndUnmarshal helper in internal/adapter/ #237 — callAndUnmarshal helper (merged ✓)
• refactor: consolidate safeSSABuild into a shared package #238 — safeSSABuild consolidation (merged ✓)
• snake-eyes PR feat: Gaze OpenCode integration, release pipeline, and distribution (Spec 005) #10 — classify_signals shipped; test_mapping is next
• website#227 — inaccurate quality docs to fix