feat(guardrails): steering channel + shell-in-file rule + capability-gap detector

Bundles three operator-reliability guardrails (Vikunja #28/#29/#30) plus the
in-flight branch WIP they were built on top of (reasoning_content capture,
operator/project profile editor, write-jail workspaceRoot fix) — the tree is
interdependent (SessionOrchestrator references reasoningArtifactId from the WIP)
and does not compile as separable subsets, so it lands as one commit.

Guardrails:
- #28 mid-stage steering: ClientMessage.SteerSession -> GlobalStreamHandler ->
  orchestrator.submitSteering, reusing SteeringNoteAddedEvent + existing context
  fold (advisory, non-authoritative; invariants #3/#7). Closes the gap where
  steering typed off an approval gate was silently dropped.
- #29 shell-in-file guardrail: ShellInFileContentRule (core:toolintent) blocks a
  file_write whose content is a bare shell command (e.g. "mkdir -p ..."); FileWriteTool
  description now advertises auto-mkdir of parent dirs. Basename-allowlist so the
  extensionless case is caught; scripts/Makefiles/multiline exempt.
- #30 pt1 capability-gap detector: deterministic CapabilityGapDetector maps stage
  intent -> implied ToolCapability, compares to granted tools, emits advisory
  CapabilityGapDetectedEvent in FreestyleDriver.lockAndRun. Recorded, never fails
  the gate and never auto-grants (invariants #3/#4/#5). Reflection rung is pt2.

Verified: ./gradlew check green (whole tree).

infrastructure/tools/filesystem/src/main/kotlin/com/correx/infrastructure/tools/filesystem/FileWriteTool.kt

@@ -39,7 +39,9 @@ class FileWriteTool(
     private val normalizedAllowedPaths: Set<Path> = allowedPaths.map { it.normalize().toAbsolutePath() }.toSet()
 
     override val name: String = "file_write"
-    override val description: String = "Write content to a file at the specified relative path (creates or overwrites)"
+    override val description: String = "Write content to a file at the specified relative path (creates or overwrites). " +
+        "Writing to a nested path auto-creates any missing parent directories — there is no separate " +
+        "mkdir step. Do not write shell commands into a file's content."
     override val parametersSchema: JsonObject = buildJsonObject {
         put("type", "object")
         putJsonObject("properties") {