feat(tcl): add dynamic argument completion and snippets

The changes add dynamic, semantic argument completion for Tcl
commands and snippet support.

- Introduces DynamicCompletionKind, TclArgumentCompletion, and dynamic rules
  for Tcl to provide variable, procedure, namespace, and path suggestions.
- Adds snippet-backed commands and arguments for Tcl blocks and paths.
- Refactors tcl_argument_completion and updates the LSP to use dynamic path,
  variable, and namespace completions with snippet kinds.

server/src/tools/variable_index.py

@@ -1,9 +1,9 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from typing import Dict, List, Set
 
 from tclint.syntax_tree import Command, Node, Script
+from tclint.syntax_tree import List as TclList
 
 
 @dataclass
@@ -18,13 +18,14 @@ def _normalize_var_name(raw_name: str | None) -> str | None:
         return None
 
     base = raw_name.split("(", 1)[0]
-    if base.startswith("::"):
-        base = base[2:]
+    base = base.removeprefix("::")
 
     return base or None
 
 
-def build_variable_index(source: str, tree: Node | None = None) -> tuple[Set[str], Dict[str, Set[str]], List[ProcRange]]:
+def build_variable_index(
+    source: str, tree: Node | None = None
+) -> tuple[set[str], dict[str, set[str]], list[ProcRange]]:
     """
     Parse Tcl source text and build:
     - globals: set of variable names considered global suggestions
@@ -40,9 +41,9 @@ def build_variable_index(source: str, tree: Node | None = None) -> tuple[Set[str
     """
     _ = source  # Kept for signature compatibility with callers.
 
-    globals_set: Set[str] = set()
-    procs: Dict[str, Set[str]] = {}
-    proc_ranges: List[ProcRange] = []
+    globals_set: set[str] = set()
+    procs: dict[str, set[str]] = {}
+    proc_ranges: list[ProcRange] = []
 
     if tree is None:
         return globals_set, procs, proc_ranges
@@ -54,7 +55,16 @@ def build_variable_index(source: str, tree: Node | None = None) -> tuple[Set[str
             if routine == "proc" and len(node.args) >= 3 and isinstance(node.args[2], Script):
                 proc_name = _normalize_var_name(getattr(node.args[0], "contents", None))
                 if proc_name is not None:
-                    procs.setdefault(proc_name, set())
+                    local_variables = procs.setdefault(proc_name, set())
+                    for parameter in getattr(node.args[1], "children", []):
+                        parameter_node = parameter
+                        if isinstance(parameter, TclList) and parameter.children:
+                            parameter_node = parameter.children[0]
+                        parameter_name = _normalize_var_name(
+                            getattr(parameter_node, "contents", None)
+                        )
+                        if parameter_name is not None:
+                            local_variables.add(parameter_name)
                     proc_ranges.append(
                         ProcRange(
                             name=proc_name,