Adds support for regex patterns in step-level glob and exclude fields,
allowing more complex file filtering patterns beyond glob patterns.

Usage:
```pkl
exclude = new Mapping {
  ["_type"] = "regex"
  ["pattern"] = #".*\.test\.js$"#
}
```

The Pattern type in Rust now supports both glob patterns (as Vec<String>)
and regex patterns (as a Regex variant with a pattern string). The
implementation uses the regex crate for pattern matching.

Changes:
- Added Regex typealias to pkl/Config.pkl
- Updated Step.glob and Step.exclude to accept Pattern enum
- Implemented Pattern enum with Globs and Regex variants
- Added custom deserializer for Pattern to handle both formats
- Extended glob::get_pattern_matches() to support regex matching
- Added comprehensive bats tests for regex patterns

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Co-Authored-By: Claude <[email protected]>

Due to Pkl's type system limitations, we can't create a Regex() function
that works directly in union types. The new Mapping syntax is required.

However, users can create their own local helper function to simplify
the syntax in their own hk.pkl file:

```pkl
local Regex = (pattern) -> new Mapping {
    ["_type"] = "regex"
    ["pattern"] = pattern
}
```

Added documentation showing this pattern as an optional convenience.

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Co-Authored-By: Claude <[email protected]>

When dir is set, regex patterns in glob and exclude are now applied
to paths relative to that directory, matching the behavior of glob
patterns. Previously, regex patterns were applied to full paths,
causing unexpected matches or misses.

For example, with dir="src" and exclude regex "^test\.js$":
- Before: Would not match "src/test.js" (regex applied to full path)
- After: Correctly matches "src/test.js" (regex applied to "test.js")

Changes:
- Added dir parameter to glob::get_pattern_matches()
- Strip dir prefix from paths before applying regex patterns
- Updated all call sites to pass dir when available
- Added test for nested directory exclusion patterns
- Fixed Pkl type annotations (Regex -> RegexPattern)

💘 Generated with Crush
Co-Authored-By: Crush <[email protected]>

Replace all instances of the `new Mapping { ["_type"] = "regex" ... }`
syntax with the cleaner `Config.Regex()` helper function.

Changes:
- Updated docs/configuration.md to import Config.pkl and use Config.Regex()
- Updated test/regex_patterns.bats to use Config.Regex() in all test cases
- Updated helper function documentation to show proper import usage

The Regex() helper must be accessed via Config.Regex() since Pkl functions
aren't automatically inherited by amending modules.

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Co-Authored-By: Crush <[email protected]>

Added tests for:
1. Glob pattern scoping with dir parameter - verifies that glob
   patterns are properly scoped to step directories in files_in_
   contention detection
2. Additional regex pattern tests with directories and nested paths

Note: User config tests with .hkrc.pkl would require a separate Pkl
schema for UserConfig which doesn't currently exist. The Rust changes
to support Pattern in UserStepConfig are verified through unit tests.

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Co-Authored-By: Claude <[email protected]>

This commit addresses several issues with glob and regex pattern matching:

1. **Pre-filter files by dir**: get_pattern_matches now pre-filters files
   by the dir parameter before applying pattern matching. This ensures
   files outside the dir are excluded, and regex patterns match against
   paths relative to the dir.

2. **Filter files when dir is set without glob**: In step_group.rs,
   steps with dir but no glob pattern now correctly filter files to
   that directory. Previously, all files were returned.

3. **Populate {{globs}} for regex patterns**: The {{globs}} template
   variable is now populated with the regex pattern string for
   Pattern::Regex, instead of being left empty. This allows templates
   to access pattern information regardless of pattern type.

Added comprehensive bats tests covering:
- Dir pre-filtering for both glob and regex patterns
- Steps with dir but no glob pattern
- {{globs}} template variable with regex patterns
- Regex patterns matching relative paths when dir is set

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Co-Authored-By: Claude <[email protected]>

Added documentation for 5 builtins that were missing from docs/builtins.md:
- check_added_large_files: Prevent committing large files (default limit: 500KB)
- detect_private_key: Detect accidentally committed private keys
- no_commit_to_branch: Prevent direct commits to protected branches
- python_check_ast: Validate Python syntax by parsing the AST
- python_debug_statements: Detect debug statements (pdb, breakpoint) in Python code

This fixes the docs:sync CI check failure.

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Co-Authored-By: Claude <[email protected]>

This reverts the problematic path manipulation introduced in commit 915223d
which broke glob matching semantics and file contention detection.

**The Bug:**
Commit 915223d changed `get_pattern_matches` to strip directory prefixes,
match against relative paths, then reconstruct full paths. This caused:

1. **Breaking semantics**: Existing patterns that relied on full path
   matching stopped working correctly
2. **Path reconstruction errors**: The join operation could create incorrect
   paths in edge cases
3. **File contention detection failures**: The code expects full paths for
   lock coordination, but received relative paths, breaking the HashSet
   comparison in step.rs:394

**The Fix:**
Reverted to the correct approach from commit 9d46cb0:
- Pre-filter files to those in `dir`
- Prefix glob patterns with `dir` (e.g., `*.rs` → `src/*.rs`)
- Match against full paths
- Return full paths consistently

This ensures file paths remain consistent throughout the system and file
locking/contention detection works correctly.

**Test Coverage:**
Added test/glob_dir_bug.bats with tests for:
- Glob path semantics with dir parameter
- Pattern matching with nested directories
- File contention detection with dir-scoped steps

All existing tests pass (299 tests total).

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Co-Authored-By: Claude <[email protected]>

This commit fixes all CI test failures on the feat/regex-patterns branch:

**Missing Util Commands:**
- Registered 5 util commands that existed as Rust files but weren't accessible:
  - check-added-large-files
  - detect-private-key
  - no-commit-to-branch
  - python-check-ast
  - python-debug-statements
- Added module imports, enum variants, and match arms in src/cli/util/mod.rs

**no_commit_to_branch Fixes:**
- Changed from `git rev-parse --abbrev-ref HEAD` to `git symbolic-ref --short HEAD`
  to support repos without commits (src/cli/util/no_commit_to_branch.rs:38)
- Fixed test to use sandbox by adding `files = List("{{tmp}}/.gitkeep")`
  and initializing git repo in `before` command (pkl/builtins/no_commit_to_branch.pkl)

**Test Fixes:**
- Updated dir.bats to use `**/*.html` and `**/*.ts` instead of `*.html` and `*.ts`
  for correct recursive matching with literal_separator=true (test/dir.bats:20)

**Test Runner Enhancement:**
- Added capture and display of `before` command output in test results
  for easier debugging (src/test_runner.rs:177-278)

All 299 tests now pass.

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Co-Authored-By: Claude <[email protected]>

- Use std::io::Error::other() instead of Error::new(ErrorKind::Other, ...)
- Remove unnecessary reference in .args(&[...]) -> .args([...])

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Co-Authored-By: Claude <[email protected]>