fix(llm-security): YAML/workflow parser divergence — block scalars + bare if: (#32,#33,#43)

#33 the frontmatter parser collected a block-scalar body (description: |) but did not skip it, so an indented name:/allowed_tools: inside the body re-matched as a top-level key and overrode the real values TRG-shadow and permission checks depend on; the parser now consumes block-scalar bodies as opaque content. #32 block-scalar headers carrying indentation/chomping indicators (|2, >-, |-2) were not recognized, so their bodies never reached the run: injection sink; now matched via a proper indicator/chomping regex.

#43 the B4 actor auth-bypass detector inspected only braced ${{ }} expressions, missing the canonical bare 'if: github.actor == ...' form (Synacktiv Dependabot-spoof false negative); bare if: expressions now emit a synthetic event the detector reads. Suite 2004/0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Claude-Session: https://claude.ai/code/session_01TcQyMTQfyrsAapaCMPxTtQ

tests/fixtures/workflows/.github/workflows/auth-bypass-bare-if.yml

@@ -0,0 +1,14 @@
+name: dependabot trust check (bare if — Synacktiv 2023)
+on:
+  pull_request_target:
+    branches: [main]
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - name: Checkout PR
+        uses: actions/checkout@v4
+      - name: Approve
+        run: gh pr review --approve

tests/fixtures/workflows/.github/workflows/tp-block-scalar-indent.yml

@@ -0,0 +1,13 @@
+name: issue triage (block scalar with indentation indicator)
+on:
+  pull_request_target:
+    branches: [main]
+
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Echo title
+        run: |2
+          echo "Issue title:"
+          echo "${{ github.event.issue.title }}"