svg-maker: svgc - .svgd text format -> SVG for agent-helm sharing

Line-based DSL (shapes, text, groups, color vars) with strict
validation and line-numbered errors, SVG emitter with visibility
defaults, truecolor terminal preview (same half-block technique as
spritec), info with bbox + outside-canvas warnings. Verified
end-to-end: svgc build -> helmd share -> visible through the hub.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011KikHkfCiC3yELbsMN8fT9

svg-maker/examples/gauge.svgd

@@ -0,0 +1,12 @@
+# gauge.svgd - example: a small status card
+canvas 240 120
+bg #12161f
+
+def ok    #3fca7c
+def frame #262d3a
+
+rect 8 8 224 104 fill=none stroke=$frame stroke-width=2 rx=10
+circle 40 60 22 fill=none stroke=$ok stroke-width=6
+path M30,60 L38,68 L52,50 stroke=$ok width=5 linecap=round fill=none
+text 76 54 "backups" size=13 fill=#8a93a5
+text 76 76 "all green" size=17 fill=white bold