feat(cardwire-cli): add a cardwire launch program

[luytan]

Description

Launch a program with cardwire ENVs using the switcheroo shim

TODO

• Copy-Paste this line

Checklist:

• My code follows the style guidelines of this project (cargo fmt)
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the mdBook documentation
• My changes generate no new warnings (clippy/clang)
• New and existing unit tests pass locally with my changes (either use nix flake check or wait for the ci)

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Repository UI

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Reviewing files that changed from the base of the PR and between 973c6c7 and 22c9cc1.

📒 Files selected for processing (1)

• crates/cardwire-cli/src/main.rs

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📝 Walkthrough

Summary by CodeRabbit

• New Features
  • Added a launch command for running programs with a selected GPU.
  • Supports choosing a GPU by ID or automatically selecting a preferred available option.
  • Preserves GPU-specific environment settings when launching programs.
  • Supports program names and arguments beginning with hyphens.
  • Reports launch failures and unsuccessful program exits.

Walkthrough

The CLI adds a Launch command. It reads SwitcherooControl GPU metadata, selects a requested or preferred GPU, applies its environment variables, and launches the specified program. Successful launches currently return a “No matching GPU found” error.

Changes

GPU-aware launch

Layer / File(s)	Summary
Launch command contract crates/cardwire-cli/src/args.rs	Adds Commands::Launch with optional --gpu selection and trailing program arguments.
GPU discovery and process launch crates/cardwire-cli/src/dbus.rs, crates/cardwire-cli/src/main.rs	Queries SwitcherooControl, parses GPU metadata, selects a GPU, applies paired environment variables, launches the program, and reports launch or exit failures. A successful launch returns an incorrect “No matching GPU found” error.

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

Sequence Diagram(s)

sequenceDiagram
  participant CLI as cardwire CLI
  participant DaemonClient
  participant SwitcherooControl
  participant Program as Requested program
  CLI->>DaemonClient: get_gpu_switcheroo()
  DaemonClient->>SwitcherooControl: Read GPUs property
  SwitcherooControl-->>DaemonClient: GPU property maps
  DaemonClient-->>CLI: GPU metadata
  CLI->>Program: Launch with selected GPU environment and arguments
  Program-->>CLI: Exit status

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Possibly related PRs

• OpenGamingCollective/cardwire#144: Modifies the same GPU metadata and environment-variable flow.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: adding a cardwire launch program to the CLI.
Description check	✅ Passed	The description summarizes the feature, states its motivation, and includes the TODO and checklist sections.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@crates/cardwire-cli/src/main.rs`:
- Around line 329-339: Update the launch command flow in main to return a
failure result when the child process exits unsuccessfully, command.status()
fails, no GPUs are found, or the --gpu selection matches no entry; preserve
successful execution as Ok(()) and propagate an appropriate error status for
each failure branch.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 8d21780b-fc0d-452f-ba11-f0a8fd86e091

📥 Commits

Reviewing files that changed from the base of the PR and between df02ca6 and 973c6c7.

📒 Files selected for processing (3)

• crates/cardwire-cli/src/args.rs
• crates/cardwire-cli/src/dbus.rs
• crates/cardwire-cli/src/main.rs