Centralize Type Definitions

Centralize types in src/types.ts with strict TypeScript enforcement

Type-safe systems with strict indexed access guards when runtime errors from undefined array access must be eliminated at compile time.

• · Project with tsconfig noUncheckedIndexedAccess enabled

• · src/types.ts with all domain, UI, session, analysis, stats types
• · No type defined outside types.ts file
• · Type guards enforcing undefined checks on indexed access
• · npm run typecheck passes with zero errors

• · TypeScript 5+
• · Biome linter (for 2-space indent, single quotes)

• · TypeScript project with strict mode enabled
• · tsconfig.json with noUncheckedIndexedAccess: true
• · src/types.ts file exists and is writable

• · Type defined outside types.ts = import fails or linter error
• · any used anywhere = typecheck error (zero tolerance)
• · interface instead of type = convention violation
• · Non-null assertion (!) used = defeats undefined checks
• · Indexed access without guard = 'T | undefined' required

• · Enforces zero 'any' usage (compile-time catch)
• · Requires explicit guards for indexed access (no ! assertions)
• · Type catalog documented with domain semantics
• · Single source of truth for all types (no duplication)