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).

examples/workflows/prompts/architect_freestyle.md

@@ -79,6 +79,12 @@ Emit a JSON object that validates against the `execution_plan` schema:
     decompose tasks here — task creation is out of scope for the plan.
 - Keep stages small and single-responsibility. Prefer more stages over large monolithic
   prompts.
+- **Scaffolding uses `file_write`, never a network installer.** A stage that sets up a project
+  writes `package.json`, config files, and sources directly with `file_write` — it does not
+  shell out to `npm create vite`, `create-react-app`, `npx`, or any `create`/`init` scaffolder.
+  Those fetch remote code and prompt on stdin; the run is unattended (no TTY) so they hang, and
+  `shell` rejects them outright. `shell` in a scaffold stage is for `npm install` / `npm run
+  build` on files that already exist, not for generating the project.
 
 **edges** — describe every transition between stages. Rules:
 - `from` and `to` must each be a declared stage `id` or the literal string `"done"`.