feat(labels): per-label outline + glow effects with DebugPanel tuning

[rulkens]

Summary

Implements the Label Text Effects plan — adds per-label outline (hard outside stroke) and glow (soft outside halo) effects to the MSDF text renderer.

• Per-label opt-in fields on Label: outlineColor?, outlineEmFrac?, glowColor?, glowEmFrac?. Defaults are zero/transparent so existing producers render unchanged.
• Straight-RGBA migration of Label.color — renderer now premultiplies at the pack-loop boundary; producers spell colours the natural way.
• Atlas rebake at distanceRange = 16 (up from 4) so the SDF carries headroom for the up-to-12-px glow falloff tail.
• Three-band fragment composite over(glow, over(outline, fill)) in premultiplied space. Overlapping bands (glow from glyph edge, outline overlays inner portion).
• Quad expansion shader-side: the vertex stage grows each corner outward by max(outlineEmFrac, glowEmFrac) * ATLAS_EM_PX so the effect bands aren't clipped.
• Live-tuning hook: labelStyleOverride module-scoped record + a category dropdown + four controls in a new LabelEffectsSection of the DebugPanel. Monotonic version counter feeds the label director's signature hash so slider edits force a re-flush.

Architecture summary

Layer	Change
Type (Label.d.ts)	+4 optional fields, color docstring updated to straight-RGBA
Renderer CPU (labelRenderer.ts)	LABEL_DATA_BYTES 48 → 96; pack loop writes 24 slots/label with premultiplication
Shader struct (io.wesl)	LabelData grows to 6 vec4s; VsOut carries outlineColor/glowColor/widths
Vertex (vertex.wesl)	Quad expansion by effect fringe; em-fraction → SDF-units conversion
Fragment (fragment.wesl)	Three-band composite with (1 - fillMask) masking on outline
Producers	youAreHereSubsystem, poiSubsystem consult labelStyleOverride per frame
Director	signatureOf includes override version so edits force re-flush
Debug UI	New LabelEffectsSection with category dropdown + 4 controls

Test plan

• Typecheck: npm run typecheck — clean ✅
• Tests: npx vitest run — 1647/1647 pass ✅
• Production build (WESL compile gate): npm run build — succeeds ✅
• Visual verification — please run the dev server and:
  • Open the DebugPanel ("Skymap Debug"); expand "Label Effects".
  • Pick cluster as the target, adjust the outline-width slider; cluster labels (Coma, Virgo, etc.) gain a visible outline within one frame.
  • Switch target to youAreHere; the cluster outline disappears, the "You are here" label gains the outline.
  • Move target back to (off); every label should look identical to its pre-feature appearance.
  • Watch for: clipped halos at the glyph quad edge, missing fill colour, label aliasing past ~60 px em height.

Out of scope (deferred follow-up)

• Baking the user's tuned values into POI_STYLES.* and youAreHereSubsystem's constants — a one-line-per-category edit that ships as a separate PR after visual tuning.
• Removing the deprecated Label.pixelSize field (still required at the type level; ignored everywhere). Separate cleanup PR.

🤖 Generated with Claude Code

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	skymap	110bf7b	Commit Preview URL Branch Preview URL	May 20 2026, 12:58 AM