gap: .t27 has no cross-module imports for user functions — every spec re-defines the ternary primitives #1773

Each spec in specs/ternary/ (majority, xor, full_adder, …) re-defines the same primitives (tmul, dot27, quantize, pack2/3, sign0, negate, bneuron). There is no way to use another user spec's functions, so a real composable library isn't possible — larger compositions (multi-bit adders, layers) must copy ~40 lines of primitives.

use base::types exists for the built-in base/isa modules, but not for user .t27 modules under specs/. A cross-module use ternary::mac (or similar) that pulls in another spec's fns would let the stack compose without duplication. Filing as a reuse/ergonomics gap for the spec-first library.

User Scenarios

• Given a user spec specs/ternary/mac.t27 defining fn tmul and fn dot27, When another spec specs/ternary/full_adder.t27 writes use ternary::mac, Then full_adder.t27 can call tmul and dot27 without re-defining them.
• Given the existing use base::types works for built-in modules, When a user writes use ternary::primitives for a local spec, Then the compiler resolves the path under specs/ and makes the fns available.

Requirements

• FR-001: The compiler MUST accept use <module>::<name> where <module> maps to a .t27 file under specs/.
• FR-002: Imported fn declarations MUST be type-checked and available in the importing spec's namespace.
• FR-003: Circular imports between user specs MUST be rejected with a clear error.
• FR-004: The use syntax for user modules MUST follow the same semantics as use base::types (no code duplication, single definition).

Success Criteria

• t27c specs/ternary/full_adder.t27 compiles with use ternary::primitives and exits 0.
• bootstrap/tests/fixtures/trinity_matrix/imports.t27 gains a test case for cross-spec use and the test suite passes (5 tests).
• No fn tmul/fn dot27/etc. definitions appear in specs/ternary/full_adder.t27 (verified by grep count = 0).

Boundary

• compiler/cli/spec.t27
• bootstrap/tests/fixtures/trinity_matrix/imports.t27
• bootstrap/tests/fixtures/trinity_matrix/functions.t27