feat(ttp): inspector drawer surfaces evidence + rule_id behind each technique

The TTPsObservedSection rollup tells the operator "we saw T1059" but
not why. Click any technique row → side drawer opens listing every
ttp_tag row in scope with the persisted evidence JSON, firing
rule_id / rule_version, source_kind / source_id, confidence, and
created_at. Mirrors the CredentialReuseInspector / BountyInspector
pattern (drawer-backdrop + bd-head/bd-body + kvs grid).

Backend:
- New `GET /api/v1/ttp/tags/by-{scope}/{uuid}/{technique_id}`
  (`scope ∈ {identity, attacker, session}`, optional
  `?sub_technique_id=`, `?limit=` capped to 1000). Returns raw
  TTPTag rows newest-first.
- New `TTPTagDetailRow` Pydantic model + re-export.
- New repo method `list_tags_by_scope_and_technique` on
  TTPMixin (+ abstract on BaseRepository) — single query branched
  on scope; identity scope projects through `Attacker.identity_id`
  the same way `list_techniques_by_identity` does.
- Tests: evidence round-trips, sub_technique filter, JWT-required,
  empty scope, unknown scope rejected.

Frontend:
- New `TTPInspector.tsx` + `TTPInspector.css` (violet accent, slide
  animation, focus-trapped panel matching the existing inspector
  family).
- `TTPsObservedSection`'s TechniqueBar is now click+keyboard
  activatable; clicking opens the inspector for that
  (technique, sub_technique) tuple.

mypy clean. 532 passed in the targeted sweep.

decnet/web/db/repository.py

@@ -1377,6 +1377,25 @@ class BaseRepository(ABC):
         """Session-scoped TTP timeline."""
         raise NotImplementedError
 
+    @abstractmethod
+    async def list_tags_by_scope_and_technique(
+        self,
+        *,
+        scope: str,
+        uuid: str,
+        technique_id: str,
+        sub_technique_id: Optional[str] = None,
+        limit: int = 200,
+    ) -> list[dict[str, Any]]:
+        """Raw ``ttp_tag`` rows backing the operator inspector.
+
+        Surfaces evidence + rule_id / source_kind / source_id so the
+        UI can show *why* the engine flagged a technique. Filtered by
+        scope (identity / attacker / session) + technique
+        (+ optional sub_technique). Newest-first.
+        """
+        raise NotImplementedError
+
     @abstractmethod
     async def list_distinct_techniques(self) -> list[TechniqueRollupRow]:
         """Fleet-wide distinct-technique rollup."""