fix(cli): surface physical deploy diagnostics

[zackees]

Summary

• replay daemon stdout/stderr for physical deploys, not only emulator routes
• send final deploy diagnostics directly to stderr so default filtering and --quiet cannot hide actionable failures
• flush stdio before non-zero process exit
• add a real CLI/mock-daemon regression test for piped stdout and stderr

Hardware context

A zero-button RP2040 deploy against the attached RPI-RP2 device exited 1 after the Windows UF2 transport failed, but the CLI hid the daemon's actionable error. This change makes the next attached-board run diagnostic without changing deployment strategy or embedding USB IDs.

Validation

• soldr cargo test -p fbuild-cli --test test_emu_exit_code
• soldr cargo test -p fbuild-cli
• soldr cargo fmt --all -- --check
• soldr cargo clippy -p fbuild-cli --all-targets -- -D warnings
• independent Rust review: one stdout flush finding, resolved and regression-tested

Supports #1049 and #1040.

Summary by CodeRabbit

• Bug Fixes
  • Deploy operations now consistently display their output and diagnostics across all deployment routes.
  • Final success and failure messages remain visible during piped, automated, quiet, and non-zero exit scenarios.
  • Improved error visibility helps preserve actionable transfer details when deployments fail.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 9274997c-5fa6-4751-a909-5ab517d114e8

📥 Commits

Reviewing files that changed from the base of the PR and between 7ea127e and 4730715.

📒 Files selected for processing (3)

• crates/fbuild-cli/src/cli/deploy.rs
• crates/fbuild-cli/src/output.rs
• crates/fbuild-cli/tests/test_emu_exit_code.rs

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📝 Walkthrough

Walkthrough

The deploy CLI now prints operation streams for all routes, routes final daemon stderr through a direct diagnostic sink, flushes both streams before non-zero exit, and adds an integration test for failed deploy output preservation.

Changes

Deploy output preservation

Layer / File(s)	Summary
Diagnostic output routing crates/fbuild-cli/src/output.rs, crates/fbuild-cli/src/cli/deploy.rs	Adds the direct diagnostic stderr helper and uses it for final daemon operation errors.
Deploy failure output handling crates/fbuild-cli/src/cli/deploy.rs, crates/fbuild-cli/tests/test_emu_exit_code.rs	Prints streams for every deploy route, flushes output before failure exit, and verifies stdout, stderr, and non-zero status with a mock deploy failure.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant fbuild
  participant MockDaemon
  participant stdout
  participant stderr
  fbuild->>MockDaemon: POST /api/deploy
  MockDaemon-->>fbuild: Failed response with stdout and stderr
  fbuild->>stdout: Print operation stdout
  fbuild->>stderr: Print diagnostic stderr
  fbuild->>stdout: Flush stdout
  fbuild->>stderr: Flush stderr
  fbuild-->>MockDaemon: Exit non-zero

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rp2040-deploy-failure-output

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