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, 21 insertions, 0 deletions

diff --git a/mingling_picker/src/builtin/pick_flag.rs b/mingling_picker/src/builtin/pick_flag.rs
new file mode 100644
index 0000000..b642a9a
--- /dev/null
+++ b/mingling_picker/src/builtin/pick_flag.rs
@@ -0,0 +1,21 @@
+use crate::parselib::{FlagMatcher, Matcher};
+use crate::pickable_needed::*;
+use crate::value::Flag;
+
+impl<'a> Pickable<'a> for Flag {
+    fn get_attr(_: &'a PickerArg<'a, Self>) -> PickerArgAttr {
+        PickerArgAttr::Flag
+    }
+
+    fn tag(ctx: TagPhaseContext) -> Vec<usize> {
+        FlagMatcher::match_all(ctx.into())
+    }
+
+    fn pick(raw_strs: &[&str]) -> PickerArgResult<Self> {
+        if raw_strs.is_empty() {
+            PickerArgResult::Parsed(Flag::Inactive)
+        } else {
+            PickerArgResult::Parsed(Flag::Active)
+        }
+    }
+}