feat(def_flow): recognize .def names propagated via variables and wrapper procs

Add a new def_flow analysis module that follows .def block template
and address names through local variables and proc parameters, and a
wrapper-table builder to resolve proc arguments that forward .def names.
Derived names are resolved only for hover/definition (not for rename).

Integrate this into the LSP:
- lsp_server: add _word_at and _tcl_def_symbol helpers; fallback to
  derived_def_symbol when direct NX-argument navigation fails for hover,
  goto-definition and references; return proper ranges for hover.
- lsp_tclserver: cache and expose a def_wrapper_table built from index
  def_flows (with cache invalidation on index generation).

Also add unit tests for def_flow and update CHANGELOG to note hover/
definition and completion preview improvements for derived names.

CHANGELOG.md

@@ -11,6 +11,8 @@ Versions correspond to the Git tags of this repository.
 - Hover over block templates shows the template body; hover over addresses shows format, leader, trailer, min/max, and modality
 - Find References and Rename for block templates and addresses across Tcl and `.def` files, including addresses used inside block templates
 - Go to Definition, hover, references, and rename also work inside `.def` files
+- Hover and Go to Definition also recognize block template and address names that reach an NX command through a local variable (`set`, `lappend`, `list`, `foreach`) or through the parameter of a custom proc such as `LIB_SPF_call_cycle "absolute_mode"`, including nested wrapper procs; same-named strings without such a path are not recognized, and these derived names are not renamed
+- Completion items for block templates and addresses (`BLOCK_LIST`, `ADDR_LIST`, `MOM_do_template`, ...) show the same preview as the hover
 
 ### Documentation