refactor(#3309): add health-diagnostic.cts skeleton (types + evaluator)

Phase 11 of epic #3180 (ADR-3180 §8.2/§8.3/§8.5). New src/health-diagnostic.cts:
SEVERITY/REMEDY_ACTION (7 members: 6 real repair actions + ADVISE)/REMEDY_RISK
(NONE/DESTRUCTIVE) frozen enums, Diagnostic/Remedy/Rule types, an empty RULES
table (rules land in the next commits), evaluateRules (with a duplicate-code
defense-in-depth check ahead of the lint guard), and applyRepairs (the
DESTRUCTIVE-risk-refusal dispatcher — §8.3 rule 3 — with stub handlers; real
repair bodies port in the migration step).

Six-gate .cts ripple: .gitignore, eslint.config.mjs, docs/INVENTORY.md +
manifest, CONTEXT.md glossary entry.

docs/INVENTORY-MANIFEST.json

@@ -378,6 +378,7 @@
       "graphify.cjs",
       "gsd2-import.cjs",
       "handshake-serialized.cjs",
+      "health-diagnostic.cjs",
       "hook-bus.cjs",
       "host-integration-sdk.cjs",
       "host-integration.cjs",