feat(spec): add Phase 1 formal specifications for TypeLL type system

Create the three highest-priority specification documents for TypeLL Phase 1:

1. Verification Protocol (spec/protocol/TYPELL-PROTOCOL.adoc) — defines the
   REST/JSON API schema including all 12 endpoints, request/response types,
   CheckContext routing, CheckResult schema, error codes, and security
   considerations. Documents the wire format consumed by PanLL's TypeLLCmd.res.

2. Dependent Types (spec/type-system/dependent.adoc) — formal typing rules
   for Pi types, Sigma types, type-level term arithmetic, refinement types
   with predicate decision procedures, universe polymorphism, proof obligation
   generation, and dimensional types. Maps all rules to Rust implementation.

3. Linear Types (spec/type-system/linear.adoc) — formal QTT substructural
   rules including the {0, 1, omega, n} semiring, context splitting/scaling,
   usage tracking lifecycle, linear vs affine mode semantics, and interaction
   with dependent types (erased arguments, session type linearity).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath