feat: directory listing compression — filter noise, tree format

[bug-ops]

Parent

Epic: #426

Summary

Compress ls and find outputs by filtering well-known noise directories and grouping files.

Expected Savings

50-70%.

Behavior

• Filter: target/, .git/, node_modules/, __pycache__/, .next/, dist/, build/
• Show directory-level file counts instead of expanding large directories
• Preserve structure for small directories

# Before: ls -la (200 lines with target/ contents)
# After:
src/ (15 files)
crates/ (9 dirs)
config/ (2 files)
target/ (filtered, 1.2GB)
Cargo.toml
README.md

Implementation

• DirListingFilter matching ls and find
• Configurable exclude patterns via config
• Size annotation for filtered dirs (if available)

Acceptance Criteria

• Known noise dirs filtered
• Large dirs summarized with count
• Configurable exclude list
• Unit tests