Add scoped Compass initialization

[forhappy]

Summary

• add interactive and automation-friendly compass init
• persist project-relative include/exclude scope in .compass/config.toml
• perform a forced initial build and reuse the saved scope for update, extract, and watch
• add help, completions, and user documentation
• harden root-path, portable absolute-path, and config-symlink validation

Why

Compass previously required users to repeat repository paths and exclusions for every build or watch invocation. This adds a first-run workflow that records a reviewable project scope and consistently applies it afterward.

User impact

Users can initialize an entire repository interactively with compass init, or automate a focused monorepo setup with repeatable --include and --exclude flags plus --yes. Invalid or unmatched scope fails before configuration is written, and existing configuration requires --force to replace.

Final review fixes

The final review found and addressed three edge cases:

• . and ./ now work as literal project-root directory scopes
• Windows absolute paths are rejected even when configuration is processed on Unix
• symlinked .compass configuration paths cannot escape and overwrite files outside the project root

Regression coverage also verifies interactive/non-interactive behavior, forced replacement, saved-scope reuse on update, and fail-closed invalid configuration handling.

Validation

• cargo fmt --all -- --check
• cargo test -p compass-files
• cargo test -p compass-core
• cargo test -p compass-cli --test init_cli --test update_cli --test watch_cli --test help_cli --test compass_product
• cargo clippy -p compass-files -p compass-core -p compass-cli --all-targets --no-deps -- -D warnings
• bash -n completions/compass.bash
• zsh -n completions/_compass
• git diff --check
• graphify update .