Prefer implicit engine defaults in workflow guidance

.github/aw/create-agentic-workflow.md

@@ -54,14 +54,17 @@ When the request already states a goal, infer its intent and ask only for inform
 5. **Data strategy** — ask whether GitHub data should be pre-fetched with `gh` + `jq` (DataOps default); map to `steps:`.
 6. **Guardrails** — ask whether it should block, advise, or silently log; guide toward `noop` and safe-output behavior.
 7. **Context & network** — ask about external APIs, MCP servers, and required secrets; map to `network.allowed` and `env:`.
-8. **Engine** (skip if obvious) — if ambiguous, suggest Copilot as the default.
+8. **Engine** — preserve explicit engine hints. With no engine preference or
+   engine-specific requirement, omit `engine:` and let the configured default
+   apply. If an explicit model requirement forces engine selection, try Copilot
+   first.
 9. **Confirmation** — present a structured summary before generating:
 
    ```text
    Proposed workflow:
    - Name: <workflow-id>
    - Trigger: <event + key options>
-   - Engine: <engine or default>
+   - Engine: <explicit engine or default (omitted)>
    - Tools: <tool summary>
    - Safe outputs: <list or none>
    - Network: <allowed summary>

.github/aw/designer.md

@@ -101,12 +101,16 @@ Map to:
 
 ### Phase 7: Engine (optional)
 
-Ask only if ambiguous: **"Any AI engine preference?"**
+Ask **"Any AI engine preference?"** only when the request contains ambiguous
+engine-specific hints.
 
-If no preference, suggest default:
-- "I'd suggest Copilot since you haven't mentioned a preference. Sound good?"
+If there is no engine preference or engine-specific requirement, do not suggest
+or specify an engine; omit `engine:` and let the configured default apply. If an
+explicit model requirement forces engine selection, try Copilot first and select
+another engine only when Copilot cannot satisfy that requirement.
 
-Map to `engine:` only when not default.
+Map to `engine:` only for an explicit preference or a requirement that the
+configured default cannot satisfy.
 
 ### Phase 7b: Skills, Plugins, LSP & Evals (optional)
 
@@ -153,7 +157,7 @@ Use this exact structure:
 📋 Proposed workflow:
 - Name: <workflow-id>
 - Trigger: <event + key options>
-- Engine: <engine or default>
+- Engine: <explicit engine or default (omitted)>
 - Tools: <tool summary>
 - Safe outputs: <list or none>
 - Network: <allowed summary>

.github/aw/syntax-engine.md

@@ -7,7 +7,7 @@ description: `engine:` frontmatter field detail for GitHub Agentic Workflows.
 See [syntax-agentic.md](syntax-agentic.md) for the full frontmatter field index.
 
 - **`engine:`** - AI processor configuration
-  - String format: `"copilot"` (default, recommended), `"claude"`, `"codex"`, `"gemini"`, or `"pi"`
+  - String format: `"copilot"` (current default), `"claude"`, `"codex"`, `"gemini"`, or `"pi"`. Omit `engine:` when there is no engine preference or engine-specific requirement so the configured default remains in effect. If an explicit model requirement forces engine selection, try Copilot first.
   - The experimental `opencode` engine is available through `imports: [shared/opencode.md]`; see [`smoke-opencode.md`](../workflows/smoke-opencode.md) for an example.
   - The experimental `deepseek-harness` engine is available through `imports: [shared/deepseek-harness.md]`; see [`smoke-deepseek-harness.md`](../workflows/smoke-deepseek-harness.md) for an example. It runs the developer-preview `dsh` headless profile with AWF provider routing and uses `provider/model` syntax.
   - The experimental `cursor` engine is available through `imports: [shared/cursor.md]`; see [`smoke-cursor.md`](../workflows/smoke-cursor.md) for an example. Requires the `CURSOR_API_KEY` secret. Cursor reads project rules from `.cursor/rules/*.mdc` and respects the root-level `.cursorignore` and `AGENTS.md`; both are protected in the manifest. Use `model: cursor/auto` or a specific model such as `cursor/claude-3-7-sonnet`.