fix(llm-security): v8 Phase 1 — Berry lockfile, nested-v1 recursion, per-occurrence strip attribution

Three TDD-first fixes surviving the B8 roadmap bucket (v8.0.0-plan.local.md
Phase 1, items 1-3; item 4 JAR hardening scoped out at review):

- supply-chain-recheck.mjs parseYarnLock: ported the hook's per-entry parser
  (pre-install-supply-chain.mjs) so Berry's `version: x` format (unquoted) is
  recognized alongside Classic's `version "x"` — Berry lockfiles previously
  yielded zero deps, silently missing pinned compromised packages.
- supply-chain-recheck.mjs parsePackageLock: lockfileVersion-1 fallback now
  recurses nested `dependencies`, mirroring the hook's walk() — a transitive,
  non-hoisted compromised copy below the top level was previously invisible.
- content-extractor.mjs stripInjection: attribution moved from a global
  `Set<label>` to `Set<label::lineIndex>`. The old check silenced the
  unstripped flag for ANY occurrence of a label once ANY occurrence had been
  line-redacted, so a second, cross-line-only encoded occurrence of the same
  label survived into sanitized output without being flagged.

Full suite 2019/2019 (one known-flaky timing test confirmed green in isolation).

tests/fixtures/supply-chain/yarn-berry-compromised.lock

@@ -0,0 +1,20 @@
+# This file is generated by running "yarn install" inside your project.
+# yarn lockfile v6
+
+__metadata:
+  version: 8
+  cacheKey: 10
+
+"event-stream@npm:^3.3.6":
+  version: 3.3.6
+  resolution: "event-stream@npm:3.3.6"
+  checksum: 0123456789abcdef
+  languageName: node
+  linkType: hard
+
+"lodash@npm:^4.17.21":
+  version: 4.17.21
+  resolution: "lodash@npm:4.17.21"
+  checksum: fedcba9876543210
+  languageName: node
+  linkType: hard