feat: extract RegexLib and add test suite

Package.swift

@@ -1,15 +1,12 @@
-// swift-tools-version: 6.2
-// The swift-tools-version declares the minimum version of Swift required to build this package.
-
+// swift-tools-version: 6.0
 import PackageDescription
 
 let package = Package(
-    name: "fledge-regex",
+    name: "fledge-plugin-regex",
+    platforms: [.macOS(.v13)],
     targets: [
-        // Targets are the basic building blocks of a package, defining a module or a test suite.
-        // Targets can depend on other targets in this package and products from dependencies.
-        .executableTarget(
-            name: "fledge-regex"
-        ),
+        .target(name: "RegexLib", path: "Sources/RegexLib"),
+        .executableTarget(name: "fledge-regex", dependencies: ["RegexLib"], path: "Sources/fledge-regex"),
+        .testTarget(name: "RegexTests", dependencies: ["RegexLib"], path: "Tests"),
     ]
 )

README.md

@@ -0,0 +1,134 @@
+# fledge-plugin-regex
+
+A [fledge](https://github.com/CorvidLabs/fledge) plugin for testing, matching, replacing, explaining, and escaping regular expressions from the command line.
+
+## Install
+
+```bash
+fledge plugins install regex
+```
+
+## Commands
+
+### test
+
+Test whether a pattern matches an input string. Shows matched text, offsets, and capture groups.
+
+```bash
+# Basic match
+fledge regex test '\d{3}-\d{4}' '555-1234'
+
+# Case-insensitive
+fledge regex test -i 'hello' 'Hello World'
+
+# Global (all matches) with capture groups
+fledge regex test -g '(\w+)@(\w+)' 'a@b c@d'
+```
+
+### match
+
+Find matching lines in a file or stdin. Similar to grep.
+
+```bash
+# Match lines in a file
+fledge regex match 'TODO' src/main.swift
+
+# Count matches only
+fledge regex match --count 'func\s' lib.swift
+
+# Invert match (show non-matching lines)
+fledge regex match -v '^\s*$' file.txt
+
+# JSON output
+fledge regex match --json '\d+' data.txt
+
+# From stdin
+cat log.txt | fledge regex match 'ERROR'
+```
+
+### replace
+
+Replace pattern matches in a file or stdin.
+
+```bash
+# Replace first match per line
+fledge regex replace 'foo' 'bar' file.txt
+
+# Replace all matches per line
+fledge regex replace -g 'old' 'new' file.txt
+
+# Modify file in place
+fledge regex replace -g 'v1' 'v2' --in-place config.txt
+
+# With capture group references ($1, $2, ...)
+fledge regex replace '(\w+)@(\w+)' '$2/$1' file.txt
+
+# From stdin
+echo 'hello world' | fledge regex replace 'world' 'there'
+```
+
+### explain
+
+Break down a regex pattern into human-readable tokens.
+
+```bash
+fledge regex explain '^\d{3}-\d{4}$'
+# Output:
+#   ^       start of string
+#   \d      digit [0-9]
+#   {3}     exactly 3
+#   -       literal '-'
+#   \d      digit [0-9]
+#   {4}     exactly 4
+#   $       end of string
+```
+
+### escape
+
+Escape special regex characters in a string so it can be used as a literal pattern.
+
+```bash
+fledge regex escape 'hello (world)'
+# Output: hello \(world\)
+
+fledge regex escape 'price: $5.00'
+# Output: price: \$5\.00
+```
+
+## Flags
+
+| Flag | Commands | Description |
+|------|----------|-------------|
+| `-g`, `--global` | test, replace | Find/replace all matches |
+| `-i`, `--case-insensitive` | test, match, replace | Case-insensitive matching |
+| `--count` | match | Show only match count |
+| `-v`, `--invert` | match | Show non-matching lines |
+| `--json` | match | JSON output |
+| `--in-place` | replace | Modify file in place |
+
+## Development
+
+Build:
+
+```bash
+swift build
+```
+
+Run tests:
+
+```bash
+swift test
+```
+
+## Architecture
+
+The plugin is split into two targets:
+
+- **RegexLib** (`Sources/RegexLib/`) -- Pure logic: regex compilation, pattern explanation, string escaping, argument parsing, and error types. Fully testable with no I/O.
+- **fledge-regex** (`Sources/fledge-regex/`) -- CLI entry point: color output, file I/O, stdin handling, dispatch, and help text. Imports RegexLib.
+
+Tests live in `Tests/` and cover all public RegexLib functions.
+
+## License
+
+See [CorvidLabs/fledge](https://github.com/CorvidLabs/fledge) for license information.