feat(gci): add compact filesystem listing

[isink17]

Summary

• add explicit rtk gci as a compact RTK-native filesystem listing command
• support bounded recursive listing, depth limits, basename glob filtering, hidden entries, multiple roots, and deterministic output
• list symlinks, Windows junctions, and reparse points without ever traversing them

rtk gci is intentionally an RTK-native filesystem command, not a transparent PowerShell Get-ChildItem/gci compatibility layer. Remove-Item is unchanged.

CLI

rtk gci [PATH...] [-a|--all] [-R|--recursive] [--max-depth N] [--filter GLOB] [--limit N]

Output is compact and machine-friendly:

• d <path> — directory
• f <bytes> <path> — regular file
• l <path> — symlink/reparse point

Safety and behavior

• filesystem paths only; no PowerShell providers or runspace semantics
• non-recursive by default
• no .gitignore or repository-aware filtering
• hidden names and Windows hidden attributes are excluded by default
• symlinks, junctions, and reparse points are listed but never traversed
• traversal is iterative
• retained result memory is bounded by --limit
• default display limit is 200 entries; truncation reports shown/total/omitted
• partial enumeration failures report the failing path, preserve successful output, and return non-zero
• no savings telemetry is recorded because this RTK-native command has no measured native-output baseline

Validation

• rtk cargo test --bin rtk gci: 58 passed, 2534 filtered
• rtk cargo fmt --all -- --check: passed
• rtk cargo check --all-targets: passed
• rtk cargo clippy --all-targets: passed
• rtk cargo test --all: 2606 passed, 8 ignored, 1 local environment failure
• the single failing grep_no_match_emits_empty_not_a_message guard was reproduced unchanged on the exact clean base SHA; the installed C:\tools\w64devkit\bin\grep.exe rejects the existing --null option and exits 2
• supplemental full run excluding only that exact base-proven environment failure: 2606 passed, 8 ignored