Add verbose mode for dependency checking (V=1)

Addresses cubic-dev-ai review feedback about suppressed error messages
making dependency issues harder to diagnose.

Changes:
- Added V=1 flag support to show pkg-config/config-tool errors
- Default mode (V=0) remains silent for optional dependencies
- Conditional _dep_stderr variable controls stderr redirection

Usage:
  make           # Silent mode (original behavior)
  make V=1       # Verbose mode (shows all dependency errors)

Testing:
- macOS V=0: No warnings (all dependencies present)
- macOS V=1: No errors (all dependencies present)
- Lima V=0: Silent (cairo/sdl2 missing, no warnings)
- Lima V=1: Shows "Package cairo/sdl2 not found" messages

This preserves the original design goal (no warnings for optional
dependencies) while providing a debug path for diagnosing real issues.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: jserv

mk/deps.mk

@@ -8,17 +8,28 @@
 # 1. Try package-config tool first (e.g., sdl2-config) - single package only
 # 2. Fall back to pkg-config if available - supports multiple packages
 # 3. Return empty string if package(s) not found
+#
+# Verbose mode: Set V=1 to show dependency-checking errors
+#   make V=1         # Show all pkg-config/config-tool errors
+#   make             # Silent mode (default)
+
+# Conditional stderr redirection based on V= flag
+ifeq ($(V),1)
+_dep_stderr :=
+else
+_dep_stderr := 2>/dev/null
+endif
 
 # Internal: Try package-specific config tool (single package only)
 # Usage: $(call _dep-config,package-name,flag-type)
 define _dep-config
-$(shell command -v $(1)-config >/dev/null 2>&1 && $(1)-config --$(2) 2>/dev/null)
+$(shell command -v $(1)-config >/dev/null 2>&1 && $(1)-config --$(2) $(_dep_stderr))
 endef
 
 # Internal: Try pkg-config (supports multiple packages)
 # Usage: $(call _dep-pkg,package-names,flag-type)
 define _dep-pkg
-$(shell pkg-config --$(2) $(1) 2>/dev/null)
+$(shell pkg-config --$(2) $(1) $(_dep_stderr))
 endef
 
 # Internal: Check if input contains multiple packages