docs: update architecture audit and roadmap for v2.7.0

Add Phase 2.7 (Deep Analysis & Graph Enrichment) covering all features
shipped since the last review: dataflow analysis, intraprocedural CFG,
AST node storage, expanded node/edge types (13 kinds, 9 edge kinds),
extractors refactoring, CLI consolidation, interactive viewer, exports
command, and normalizeSymbol utility.

Update Phase 3 priorities: add unified AST analysis framework as new #1
critical item (5,193 lines of parallel AST walking across complexity/
CFG/dataflow/ast with no shared infrastructure). Update all metrics
across Phase 3 items (50 modules, 26K lines, 13 tables, 34 MCP tools).
Mark qualified names as partially addressed (parent_id + contains edges).
Subsume standalone complexity decomposition into AST framework.

Update Phase 4 type definitions with new kind/edge type hierarchies.
Mark Phase 9.1 visualization as partially complete (plot command).

Author: carlos-alm