feat(adf): introduce unified evidence/enforcement pipeline

[SmartBrandStrategies]

Linked feedback: ADX-007

Problem

Enforcement is fragmented:

• metric/weight evidence is computed in validator.ts
• token budget/module budget checks are computed in bundler.ts

This creates multiple result shapes and multiple enforcement entry points.

Evidence:

• Metric evidence: packages/adf/src/validator.ts:27
• Bundle budget checks: packages/adf/src/bundler.ts:252

Scope

• Introduce a single evaluator API (e.g. evaluateEvidence(...)) under packages/adf/src/evidence.ts.
• Combine:
  • metric constraint results (pass/warn/fail)
  • weight summary
  • token budget utilization
  • per-module budget overruns
  • advisory-only module warnings
• Update bundler and CLI evidence flows to consume shared evaluator output.

Acceptance Criteria

• One typed result envelope is used by both bundle and evidence flows.
• Validator semantics for metric status remain backward compatible.
• No loss of fields currently emitted in bundle/evidence outputs.
• Tests cover both metric and budget enforcement in one pipeline.

Test Plan

• pnpm run test --filter @stackbilt/adf
• Add tests for:
  • under/at/over ceiling metric statuses
  • bundle token budget utilization
  • per-module budget overrun emission
  • advisory-only module warnings

[SmartBrandStrategies]

Blocked by #8 — bundler split must land first so the evidence pipeline integrates against the new merger.ts/manifest.ts boundaries rather than the monolithic bundler.