Sprint 1: project skeleton, type system, and all architecture specs

- src/types.hpp: complete UCWM type system in C++20 — 19 enums, 11 facet
  data types, all core structs (CanonicalObject, Constraint, Facet,
  GateSignal, WorldState, etc.) with full JSON round-trip serialization
- src/main.cpp: smoke test — constructs apple-problem WorldState by hand,
  serializes to JSON
- tests/test_types.cpp: 19 tests, 123 assertions, all passing
- CMakeLists.txt: CMake + CPM build with nlohmann/json, spdlog, Catch2
- schemas/: JSON Schema contracts for all UCWM data types
- gates/, specialists/, resolver/, synthesis/: language-agnostic interface
  contracts and domain specs for all pipeline layers
- docs/: architecture, vocabulary, decision matrices, roadmap (6 phases,
  28 sprints), sprint_001, implementation_constraints

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gates/registry.md

@@ -0,0 +1,70 @@
+# Gate Registry
+
+The gate registry maps gate IDs to their implementations and metadata. The registry is the authoritative list of which gates are active in the system.
+
+---
+
+## Registry entry format
+
+```
+GateRegistryEntry {
+  gate_id:          string         -- must match a standard gate_id or be a registered extension
+  display_name:     string         -- human-readable label
+  description:      string         -- one sentence on what this gate detects
+  method:           string         -- "regex" | "rule" | "classifier" | "neural" | "hybrid"
+  implementation:   string         -- reference to implementation module or file
+  version:          string         -- semver
+  enabled:          boolean        -- false to disable without removing from registry
+  recall_threshold: float [0, 1]   -- minimum recall this gate is expected to maintain
+  activates_specialists: string[]  -- hint: which specialists this gate commonly triggers
+  notes:            string?        -- optional
+}
+```
+
+---
+
+## Active gate registry (initial)
+
+These are the initial gate implementations. All use rule/regex methods as starting points. They will be upgraded to classifiers or neural models as the contract tests stabilize.
+
+| gate_id | method | activates_specialists | enabled |
+|---|---|---|---|
+| `is_math` | rule | quantity, logic | true |
+| `is_code` | rule | code | true |
+| `has_temporal_relation` | rule | temporal | true |
+| `has_spatial_relation` | rule | spatial | true |
+| `has_causal_relation` | rule | causal | true |
+| `has_entity_reference` | rule | entity | true |
+| `has_coreference` | rule | entity | true |
+| `has_quantity` | rule | quantity | true |
+| `has_logical_negation` | rule | logic | true |
+| `has_comparison` | rule | quantity, logic | true |
+| `has_planning` | rule | planning | true |
+| `has_constraint` | rule | logic, planning | true |
+| `has_state_change` | rule | ownership, temporal | true |
+| `has_ownership_transfer` | rule | ownership, entity | true |
+| `has_social_intent` | rule | social | true |
+| `requires_external_knowledge` | rule | — | true |
+| `requires_synthesis_only` | rule | — | true |
+
+---
+
+## Adding a new gate
+
+1. Define a gate ID. Use `has_{relation_family}` for relation detectors and `is_{domain}` for domain detectors.
+2. Write the implementation satisfying `gates/contract.md`.
+3. Write at least 5 positive recall tests and 5 true negative tests per `tests/contracts/gate_contract_tests.md`.
+4. Add an entry to this registry.
+5. Update `activates_specialists` with which specialists this gate commonly triggers. This is a hint to the router, not a constraint.
+
+---
+
+## Upgrading a gate implementation
+
+A gate's contract (gate_id, output schema, invariants) does not change when the implementation method changes. A regex gate may be replaced by a neural gate without any other component knowing. The registry `method` field and `version` field must be updated.
+
+---
+
+## Disabling a gate
+
+Set `enabled: false`. Do not remove entries — removal loses the `activates_specialists` hint and breaks the audit trail.