chore(v→zig): delete V-lang API layer, collapse into Zig FFI block (#72)

## Summary

Estate-wide V-lang→Zig remediation per the 2026-05-28 owner directive.

- Deletes `api/v/src/ecm_api.v` + `ecm_api_test.v` (V-lang wrappers
around the existing `ffi/zig/` adapter)
- `TOPOLOGY.md`: collapses the two-layer "V API + Zig FFI" diagram into
a single Zig API+FFI block
- `Trustfile.a2ml`: drops the V language entry; the Zig FFI is now the
canonical consumer-facing API

## Test plan

- [ ] Hypatia rule \`cicd_rules/vlang_detected\` does not flag this repo
post-merge
- [ ] TOPOLOGY.md diagram renders correctly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

TOPOLOGY.md

@@ -14,13 +14,7 @@
                                        │
                                        ▼
                     ┌─────────────────────────────────────────────┐
-                    │            zig API LAYER                  │
-                    │         api/v/src/ecm_api.v                 │
-                    │   Consumer-facing types + classification     │
-                    └──────────────────┬──────────────────────────┘
-                                       │
-                    ┌──────────────────┼──────────────────────────┐
-                    │          ZIG FFI BRIDGE                      │
+                    │          ZIG API + FFI BRIDGE                │
                     │        ffi/zig/src/main.zig                 │
                     │    C-ABI ← generated/abi/robodog_ffi.h      │
                     └──────────────────┬──────────────────────────┘
@@ -77,12 +71,10 @@ IDRIS2 ABI (src/abi/)
   Formation Types                   ███░░░░░░░  30%    Coordinates, separation proofs
   FFI Declarations                  ███░░░░░░░  30%    Zig bridge bindings
 
-ZIG FFI (ffi/zig/)
+ZIG API + FFI (ffi/zig/)
   Signal Classification             ████░░░░░░  40%    3 rules, band checking
   Distance / Separation             █████░░░░░  50%    Ground + aerial, integer math
   Formation Computation             ███░░░░░░░  30%    Line + circle, rest TBD
-
-zig API (api/v/)
   ECM API                           ████░░░░░░  40%    Full type mirror, classify, recommend
   ABI Verification Types            ███░░░░░░░  30%    Round-trip proofs
 

api/v/src/ecm_api.v

@@ -323,15 +323,8 @@ languages:
       memory_safety: "Compile-time bounds checking, no hidden allocations"
       abi_compat: "Native C ABI, zero runtime overhead"
 
-  - name: "V"
-    role: "API layer (consumer-facing)"
-    location: "api/v/"
-    components: ["ecm_api", "crypto_api", "formation_api"]
-    build: "v build api/v/"
-    test: "v test api/v/"
-    security:
-      input_validation: "All external inputs validated at API boundary"
-      abi_verification: "Types checked against Idris2 ABI definitions"
+  # V-lang API layer removed 2026-05-28; the Zig FFI at ffi/zig/ is now the
+  # canonical consumer-facing API per estate-wide Zig=APIs+FFIs policy.
 
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