feat(lsp): add Tcl command-aware completion and integration

- Introduced a Tcl command-aware completion engine and wired to LSP.
- Added a new module with Tcl commands, options, and contextual matching.
- Updated completion to favor command-aware items and args.

server/src/tools/completion_items.py

@@ -6,9 +6,11 @@ from collections.abc import Iterable, Sequence
 from enum import Enum
 
 import lsprotocol.types as lsp
-from common.load_data import standard_items
 from tclint.syntax_tree import BareWord, Command, List, Visitor
 
+from common.load_data import standard_items
+from tools.tcl_command_completion import line_prefix_at_position
+
 BUILTIN_VAR_LABELS = {ci.label for ci in standard_items.nx_variables}
 BUILTIN_PROC_LABELS = {ci.label for ci in standard_items.nx_procs}
 
@@ -35,27 +37,12 @@ _VARIABLE_PREFIX_RE = re.compile(r"(?<!\\)\$(?:\{)?[A-Za-z0-9_:]*$")
 _COMMAND_PREFIX_RE = re.compile(r"(?:^|[;\[\{])\s*[^\s;\[\]\{\}]*$")
 
 
-def _codepoint_offset(line: str, utf16_offset: int) -> int:
-    """Translate an LSP UTF-16 character offset into a Python string offset."""
-    if utf16_offset <= 0:
-        return 0
-
-    units = 0
-    for offset, character in enumerate(line):
-        units += 2 if ord(character) > 0xFFFF else 1
-        if units >= utf16_offset:
-            return offset + 1
-    return len(line)
-
-
 def completion_context(
     source_lines: Sequence[str], position: lsp.Position
 ) -> CompletionContext:
-    if position.line < 0 or position.line >= len(source_lines):
+    prefix = line_prefix_at_position(source_lines, position)
+    if prefix is None:
         return CompletionContext.GENERAL
-
-    line = source_lines[position.line]
-    prefix = line[: _codepoint_offset(line, position.character)]
     if _VARIABLE_PREFIX_RE.search(prefix):
         return CompletionContext.VARIABLE
     if _COMMAND_PREFIX_RE.search(prefix):