feat: v0.3.0 Persistent + Z-Tiers + Input-Block

Layer z_tiers (hud/normal/top), persistent windows, and input_block
routing (none/self/all) on top of v0.2.0's multi-active + layout-slot
model. Render iterates per-tier (hud->normal->top); input dispatch
iterates reverse (top->hud, within-tier reverse-open-order); modal
input_block='all' swallows misses. Persistent windows open at
register-time and are exempt from arg-less close() (so ESC and default
triggers cannot dismiss persistent toolbars/HUDs).

Adds chromeless=true opt (suppresses panel-lib's own decoration so
in-game HUD widgets like map-editor's toolbar/layers/palette can paint
their own visual style over the full widget bounds).

Adds public panel.point_in_any_panel(x, y) — module-side canvas-click
gate that returns true if (x, y) falls within any open panel's
bounds. Modules read input directly via engine.input.*; they can use
this helper to skip canvas-paint when the click landed on a panel
widget area.

manifest.lib

@@ -1 +1 @@
-{"id":"lib-core.panel","version":"0.2.0","api_min":"0.1","deps":[]}
+{"id":"lib-core.panel","version":"0.3.0","api_min":"0.1","deps":[]}