Idea: Praxis-Forge to enable shell autocompletion

[crstrn13]

Summary

Add shell autocompletion (bash, zsh, fish) for the praxis-forge CLI via a completions <shell> subcommand.

Motivation

The CLI has ~21 leaf commands across 4 subcommand groups, global flags, and enum-valued options. Shell completion would reduce friction for users who need to remember subcommand names and flag spellings.

Since the project already uses clap 4.6 with derive macros, the clap_complete crate provides first-party support with minimal effort.

Proposed Solution

Phase 1 — Static completions

• Add clap_complete as a dependency
• Add a completions <shell> subcommand that calls clap_complete::generate() for bash, zsh, fish, and PowerShell
• Derive ValueEnum on OutputFormat and RuntimeProvider (replacing manual FromStr impls) so clap can advertise their possible values (text|json, auto|docker|podman) to completion scripts

This covers all subcommands, flags, and fixed-value options.

Phase 2 (optional) — Dynamic completions

• Use clap_complete::CompleteEnv (clap 4.5+) for shell-side dynamic completion
• Wire up callbacks that read forge.yaml to suggest valid cluster, service, and stack names for positional arguments

Acceptance Criteria

• praxis-forge completions bash|zsh|fish generates a working completion script
• All subcommands and flags are completed
• --output completes to text, json; --runtime completes to auto, docker, podman
• Installation instructions in --help output or README

Alternatives Considered

• Manual completion scripts: more work to maintain and keep in sync with the CLI as it evolves.

Additional Context

• The command tree is shallow (max depth 2), so generated scripts will be compact.
• Estimated effort: ~1-2 hours for Phase 1; ~half a day for Phase 2.

Review guidance

• Focus on the completions subcommand wiring and the ValueEnum derive migration
• Verify generated scripts work in at least bash and zsh

Manual verification

1. Build: cargo build
2. Generate completions: ./target/debug/praxis-forge completions bash > /tmp/forge.bash
3. Source: source /tmp/forge.bash
4. Type praxis-forge <TAB> and confirm subcommands appear
5. Type praxis-forge --output <TAB> and confirm text / json appear

[shaneutt]

Our proposal process has been updated to no longer require discussions so we'll close this: Instead create a feature request on the repo in question and maintainers will assess 🖖