fix(engine): pass Copilot prompt using attached --prompt= form #2186

Problem

ado-aw-generated pipelines fail with Copilot CLI 1.0.84-5 through at least
1.0.86-2 when runtime imports are enabled.

ado-aw currently emits:

/tmp/awf-tools/copilot --prompt "$(cat /tmp/awf-tools/agent-prompt.md)" ...

Runtime imports insert the complete workflow Markdown file, including its YAML
frontmatter. The resulting prompt begins with ---.

Following the Copilot CLI parser migration from Commander to clap, a separately
passed --prompt value beginning with a hyphen is interpreted as another option.
The CLI exits before starting the agent and replaces the underlying parser error
with the misleading diagnostic:

error: Invalid command format.

It looks like your prompt was not quoted, so the extra words were treated as separate arguments.

The prompt is correctly quoted as one shell argument.

Reproduction

1. Compile a workflow that uses runtime imports, so the generated prompt begins
   with Markdown YAML frontmatter (---).
2. Run the generated Agent stage with Copilot CLI 1.0.84-5 or newer.
3. Observe that Copilot exits during argument parsing before the agent starts.

The underlying CLI behavior can be reduced to:

# Fails on affected versions
copilot --prompt '--- heading words' --allow-all-tools

# Parses successfully
copilot --prompt='--- heading words' --allow-all-tools

Investigation found this version boundary:

• 1.0.83: succeeds
• 1.0.84-4: succeeds
• 1.0.84-5: fails
• 1.0.85: fails
• 1.0.86-0: fails
• 1.0.86-1: fails
• 1.0.86-2: fails

Suggested fix

Generate the attached-value form:

/tmp/awf-tools/copilot --prompt="$(cat /tmp/awf-tools/agent-prompt.md)" ...

This parses successfully on tested affected versions and should remain
compatible with older versions.

Apply the same change to the Detection-stage prompt invocation.

Tests

Add a compiler or smoke regression test that:

1. Uses a prompt beginning with ---.
2. Asserts that generated Agent and Detection invocations use --prompt=.
3. Exercises the generated command against the currently pinned Copilot CLI.

Versions

• Reproduced with ado-aw 0.51.0.
• ado-aw 0.52.0 still generates the separated form.
• Last unaffected Copilot stable tested: 1.0.83.
• First affected Copilot prerelease tested: 1.0.84-5.