fix(compile): show full error chain in batch compile output

[jamesadevine]

Problem

When batch-compiling pipelines (ado-aw compile with no path), front matter parse errors only showed the outermost context message:

  Error compiling 'agents/failure-summary.md': Failed to parse YAML front matter

The underlying serde error — which names the specific unknown field and lists valid alternatives — was swallowed by the {} (Display) format.

Fix

Switch from {} to {:#} (alternate Display) for anyhow::Error, which prints the full error chain. Users now see:

  Error compiling 'agents/failure-summary.md': Failed to parse YAML front matter: unknown field `safeoutputs`, expected one of `name`, `description`, `target`, ...

The single-file compile path (ado-aw compile <file>) was already fine — its error propagates to main() where Rust's Debug formatting shows the full chain.

Change

One-character change in src/compile/mod.rs: {} → {:#} in the batch compile error eprintln!.

[github-actions]

🔍 Rust PR Review

Summary: Correct and minimal — no issues found.

Findings

✅ What Looks Good

• {:#} is exactly right for anyhow::Error: its alternate Display joins the error chain with : separators, giving users the full diagnostic without a stack trace. {:?} (Debug) would also show the chain but with a backtrace dump — {:#} is the appropriate choice for user-facing eprintln! output.
• The explanation that the single-file path already works (errors propagate to main() where Rust formats via Debug) is accurate and the fix correctly targets only the batch path.
• One-character change, zero risk of regression.

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