feat(toolintent): stage write-manifest enforcement (role-reliability §2)

Scope creep — an implementer writing files it never declared — is the
dominant local-model failure that compiler/tests don't catch. A stage can
now declare a `writes` manifest (workspace-relative globs); a FILE_WRITE
that resolves inside the workspace but outside the declared set is raised
as PATH_OUTSIDE_MANIFEST → BLOCK, so the model gets the violation as tool
feedback and retries within scope (the §2 bounded-retry signal).

Implemented as a plane-2 rule beside PathContainmentRule (same effect-based
dispatch on FILE_WRITE, same symlink-safe WorldProbe resolution, same
recorded observations so replay reads them back — invariant #9). An empty
manifest is unrestricted; out-of-workspace targets stay PathContainmentRule's
concern, so the two rules don't double-flag.

- StageConfig.writeManifest + TomlWorkflowLoader `writes` parsing
- ToolCallAssessmentInput.writeManifest, threaded from the active stage via
  SessionOrchestrator.runPlane2Assessment
- new ManifestContainmentRule, registered in the server assessor
- shared candidatePathStrings extracted so both path rules judge the same
  target set
- role_pipeline.toml documents the option on the implementer stage

The dedicated ManifestViolationEvent the spec names is not added: the
violation is already recorded replayably in ToolCallAssessedEvent (issue +
observations + BLOCK) and surfaced in the TUI rationale band. A first-class
event is worth adding only once reconciliation consumes it.

core/transitions/src/main/kotlin/com/correx/core/transitions/graph/StageConfig.kt

@@ -18,5 +18,10 @@ data class StageConfig(
     val maxRetries: Int = 3,
     val produces: List<TypedArtifactSlot> = emptyList(),
     val needs: Set<ArtifactId> = emptySet(),
+    // Workspace-relative globs the stage is permitted to write (role-reliability §2
+    // diff manifest). Empty = unrestricted within the workspace. A FILE_WRITE outside
+    // the declared set is scope creep — the dominant local-implementer failure — and is
+    // blocked by the plane-2 ManifestContainmentRule.
+    val writeManifest: List<String> = emptyList(),
     val metadata: Map<String, String> = emptyMap(),
 )