Migrate from clap to facet-args

[fasterthanlime]

Summary

• Replace clap derive macros with facet-args for CLI argument parsing
• Use git dependencies since the published version doesn't export the help module yet
• Manual --help handling added since facet-args doesn't intercept it automatically

Closes #13

Test plan

• cargo build --package fontcull-cli compiles successfully
• fontcull --help displays help text
• fontcull --unknown shows error for unknown flags

[Copilot]

Pull request overview

This PR migrates the CLI argument parsing from clap to facet-args, replacing derive macros and adding manual help text handling. The changes address issue #13 by switching to the facet ecosystem for argument parsing.

Key changes:

• Replaced clap::Parser derive with facet::Facet and updated all argument attributes
• Added manual --help handling since facet-args doesn't intercept it automatically
• Updated dependencies to use git sources for facet packages

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

File	Description
fontcull-cli/src/main.rs	Replaced clap imports and derive macros with facet equivalents, converted all argument attributes to facet syntax, and added manual help handling logic
fontcull-cli/Cargo.toml	Removed clap dependency and added git-based facet and facet-args dependencies

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[Copilot]

Git dependencies lack version pinning. Consider adding rev, tag, or branch specifiers to ensure reproducible builds and avoid unexpected breaking changes.

Suggested change

	facet-args = { git = "https://github.com/facet-rs/facet" }
	facet-args = { git = "https://github.com/facet-rs/facet", rev = "a1b2c3d4e5f6g7h8i9j0k" }

[Copilot]

The raw_args vector is collected but only used for the help check. Consider using std::env::args().skip(1).any(|a| a == \"--help\" || a == \"-h\") to avoid the unnecessary allocation.

Suggested change

	let raw_args: Vec<String> = std::env::args().skip(1).collect();
	if raw_args.iter().any(|a| a == "--help" || a == "-h") {
	if std::env::args().skip(1).any(|a| a == "--help" || a == "-h") {