Fix: rg --type gdscript is invalid — use --glob *.gd instead (#42)

* Fix: document that rg --type gdscript is invalid, use --glob *.gd instead

Closes #37. ripgrep has no gdscript type — *.gd files are registered under
the gap type (GAP programming language). Using --type gdscript produces a
hard error, silently preventing any search from executing.

Added explicit warnings in two places:
- .claude/agents/godot-gdscript-specialist.md: new Tooling section with
  the correct Grep tool param (glob: "*.gd") and shell equivalent
- docs/engine-reference/godot/current-best-practices.md: new Tooling
  section agents read at version-check time

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Fix: propagate rg --glob *.gd tooling warning to all Godot agents

Closes the coverage gap identified in PR #42 review — the ripgrep
gdscript-type warning was only in godot-gdscript-specialist. Added
the same CRITICAL tooling section to godot-specialist,
godot-gdextension-specialist, godot-shader-specialist, and
godot-csharp-specialist so no Godot agent can silently misfire a search.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/engine-reference/godot/current-best-practices.md

@@ -93,6 +93,12 @@ This supplements (not replaces) the agent's built-in knowledge.
 - Live preview in Quick Open dialog when "Live Preview" enabled
 - New "Select Mode" (v key) prevents accidental transforms; old mode renamed "Transform Mode" (q key)
 
+## Tooling
+
+- **ripgrep has no `gdscript` type**: `*.gd` is registered under `gap` (GAP programming language).
+  `rg --type gdscript` is a hard error — the search never executes.
+  Always use `rg --glob "*.gd"` (shell) or `glob: "*.gd"` (Grep tool) to filter GDScript files.
+
 ## Platform (4.5+)
 
 - **visionOS export**: First new platform since open-sourcing (windowed app mode)