refactor(halcon): single-skill plugin layout → invoke as /halcon (not /halcon:halcon)

Move SKILL.md + references/ scripts/ evals/ from skills/halcon/ up to the
plugin root. Per Claude Code plugins-reference, a plugin with SKILL.md at its
root and no skills/ subdir is auto-loaded as a single-skill plugin (v2.1.142+),
so the invocation name = frontmatter name = halcon → clean /halcon.
Bump plugin.json 2.0.0 → 2.0.1 so existing installs receive the update.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/halcon/scripts/_common.py

@@ -0,0 +1,40 @@
+"""Shared helpers for the HALCON runner scripts."""
+import re
+
+_INT_RE = re.compile(r"^[+-]?\d+$")
+_FLOAT_RE = re.compile(r"^[+-]?(\d+\.\d*|\.\d+|\d+)([eE][+-]?\d+)?$")
+
+
+def coerce(value: str):
+    """Turn a CLI string into int/float/str, or a list for comma-separated input.
+
+    Absolute paths (C:/..., /mnt/...) and anything non-numeric stay strings.
+    Use a trailing comma or commas to force a tuple, e.g. '1,2,3' -> [1,2,3].
+    """
+    if "," in value:
+        return [coerce(v) for v in value.split(",") if v != ""]
+    if _INT_RE.match(value):
+        return int(value)
+    if _FLOAT_RE.match(value) and not value.strip().startswith(("C:", "c:")):
+        return float(value)
+    return value
+
+
+def jsonable(v):
+    """Make a HALCON output control value JSON-serializable."""
+    if isinstance(v, (list, tuple)):
+        return [jsonable(x) for x in v]
+    if isinstance(v, (int, float, str, bool)) or v is None:
+        return v
+    return str(v)
+
+
+def parse_set(pairs):
+    """['Name=Value', ...] -> [(name, coerced_value), ...]."""
+    out = []
+    for p in pairs or []:
+        if "=" not in p:
+            raise SystemExit(f"--set expects Name=Value, got: {p!r}")
+        name, _, raw = p.partition("=")
+        out.append((name.strip(), coerce(raw)))
+    return out