feat: add bidirectional cross-repo linking to sigil

.gitignore

@@ -57,3 +57,6 @@ vendor.log
 
 # Claude Code local settings (environment-specific)
 .claude/settings.local.json
+
+# Rivet external project cache
+.rivet/

artifacts/architecture.yaml

@@ -61,6 +61,7 @@ artifacts:
       ARM Thumb-2 machine code encoder, ELF binary builder, vector table
       generator, linker script support, and MPU configuration. Produces
       bare-metal ELF binaries ready for flashing to Cortex-M targets.
+      ELF output is the input to sigil for supply chain signing (sigil:FEAT-2).
     status: implemented
     tags: [backend, arm-encoding, elf]
     links:
@@ -72,6 +73,12 @@ artifacts:
         target: FR-005
       - type: allocated-from
         target: FR-008
+      - type: traces-to
+        target: sigil:CR-12
+      - type: traces-to
+        target: sigil:CD-14
+      - type: traces-to
+        target: sigil:FEAT-2
     fields:
       component-type: software
       interfaces:

artifacts/nonfunctional-requirements.yaml

@@ -36,13 +36,19 @@ artifacts:
       produce deterministic output (same input yields same output), provide
       comprehensive error handling, achieve greater than 99% correctness on
       the WebAssembly test suite, and support continuous fuzzing integration.
+      Deterministic output is critical for sigil's attestation chain integrity
+      (sigil:L-7, sigil:DF-13).
     status: draft
     tags: [reliability, determinism, nonfunctional]
     links:
       - type: derives-from
         target: BR-001
       - type: derives-from
         target: BR-002
+      - type: traces-to
+        target: sigil:L-7
+      - type: traces-to
+        target: sigil:SC-14
     fields:
       req-type: constraint
       priority: must

rivet.yaml

@@ -50,3 +50,9 @@ externals:
     path: /Volumes/Home/git/pulseengine/meld
     ref: main
     prefix: meld
+
+  sigil:
+    git: https://github.com/pulseengine/sigil.git
+    path: /Volumes/Home/git/pulseengine/sigil
+    ref: main
+    prefix: sigil