feat(picker2): complete Picker2 prototype

Picker2 replaces the original Picker1 with a two-phase (tag → pick) +
mask-bitmap architecture, decoupling argument matching from type
conversion via a composable matcher pipeline.

Architecture
- FlagMatcher — boolean flags (--verbose)
- ArgMatcher — single flag+value pairs (--name Alice)
- MultiArgMatcher — multi-value flag groups (--files a.txt b.txt)
- PositionalMatcher — positional arguments, respects `--`
- SingleMatcher — composite for Single-type Pickables

Types
- Flag (Active/Inactive) — semantic bool flag value
- String + 14 numeric types via SinglePickable trait
- Vec<T> — greedy multi-value (all SinglePickable types)
- VecUntil<T> — bounded multi-value via BoundaryCheck trait
- VecUntil<T>, pick_string, pick_numbers, pick_bool, pick_flag

Style system
- UNIX_STYLE (kebab), POWERSHELL_STYLE (Pascal), WINDOWS_STYLE (Pascal)
- naming_case auto-conversion via just_fmt integration
- Style-aware separator (= for Unix, : for PS/Windows)

Infrastructure
- internal_repeat! macro generates PickerPattern1..=32
- SinglePickable blanket impl → Pickable
- MultiPickableWithBoundary trait with greedy/bounded variants
- 151 integration tests
- Docs updated for parser feature

1 files changed, 42 insertions, 0 deletions

diff --git a/mingling_picker/README.md b/mingling_picker/README.md
index e69de29..c83bff4 100644
--- a/mingling_picker/README.md
+++ b/mingling_picker/README.md
@@ -0,0 +1,42 @@
+# Mingling Picker
+
+A command-line argument parser for [Mingling](https://github.com/mingling-rs/mingling), enabled by the `mingling/picker` feature.
+
+```toml
+[dependencies.mingling]
+version = "0.3.0"
+features = [
+    "picker"
+]
+```
+
+Of course, you can also use it as a standalone crate by replacing `mingling::picker` with `mingling_picker`:
+
+```toml
+[dependencies]
+mingling_picker = "0.3.0"
+```
+
+## Chained Argument Parser
+
+Provides a clean chained-call API for declaring arguments to parse:
+
+```rust
+let args: Vec<&str> = vec!["--name", "Bob", "--age", "24"];
+let result = args
+    .pick(&flag![name: String])
+    .or(|| "Alice".to_string())
+    .pick(&flag![age: i32])
+    .or(|| 24)
+    .post(|num| num.clamp(0, 120))
+    .parse();
+let (name, age): (String, i32) = a.unwrap();
+```
+
+## Parsing Function Library
+
+Provides a pure function library `parselib` for analyzing the structure of command-line arguments.
+
+```rust
+use mingling::picker::parselib::*;
+```