Complete LTI 1.3 + Advantage Support

[eliknebel]

This PR delivers the full spec-aligned feature set (Core, Deep Linking, AGS, NRPS, OAuth/provider hardening) and adds certification governance artifacts so requirement coverage is traceable, testable, and auditable.

Core platform/tooling

• Hardened launch validation, required claim checks, audience/azp handling, nonce/state semantics, and provider
  launch-context behavior.
• Structured error modeling and conversions for consumer-facing compatibility.
• Provider contract updates for login-context and nonce correctness.
• Logger dependency migration and cleanup of prior FFI logger implementation.

Deep Linking

• New Deep Linking request decode and settings API.
• Deep Linking response JWT generation and form-post helper.
• Content-item validation and typed error paths.

AGS

• Full line item CRUD coverage.
• Score publish support.
• Results listing support.
• Scope helper/guard APIs.
• Link-header pagination support and associated error handling.

NRPS

• Spec-aligned claim decoding (context_memberships_url, service_versions).
• Scope helper/guard APIs.
• Membership retrieval with options (role/limit/rlid) and continuation helpers (next, differences).
• Tolerant member decode behavior and typed errors.

OAuth/provider improvements

• Typed token-fetch API and structured OAuth errors.
• Assertion hardening options.
• Optional token cache module for service-token reuse.

Certification package

• Conformance matrix artifact with FR/NFR + cert objective mapping.
• Certification runbook with setup, sequencing, triage, and submission checklist.
• Evidence package layout with dated dry-run records and summary rollup.
• New matrix lint automation script:
  • required columns/status validation
  • FR/NFR coverage check against epic PRD
  • reference existence checks (implementation/tests/evidence)
• CI gate update to enforce matrix lint before tests.
• Conformance-focused test modules under test/lightbulb/conformance/.