fix(core): add deterministic normalization for parallel batch analyzer output

Parallel file-analyzer subagents can produce inconsistent node IDs
(project-name prefixed, double-prefixed, bare paths) and invalid
complexity values. Phase 3 ASSEMBLE now normalizes these deterministically
before merging, preventing cascading edge drops and dashboard load failures.

- Add normalize-graph.ts with normalizeNodeId, normalizeComplexity,
  and normalizeBatchOutput utilities
- Rewrite SKILL.md Phase 3 with 6-step normalization sequence
- Strengthen file-analyzer prompt with ID format warnings
- Add 32 normalization tests and 2 schema boundary tests

Author: fishinakleinbottle