Hover-inspect tooltip — what's under the cursor

Adds an InspectTooltip CanvasLayer that follows the mouse, samples the
tile under the cursor each frame, and renders a small dark panel with a
short description of whatever's there.

Per-entity describers cover the playable surface:
* Pawn: name + HP + mood + current job
* Tree / rock / big rock: progress %, "marked" tag if designated
* Wall: material + ghost/% if unbuilt
* Floor / door / torch: ghost vs complete state
* Bed: occupant or "available", medical tag
* Crate: full contents broken down by item type and count
* Workbench: label + active bills count
* Item on ground: type + stack size
* Corpse: deceased name + fresh/rotting/rotted state
* Wolf: HP + state
* Grave marker: deceased name
* Stockpile / graveyard zone: name + priority + accepted types

Layer 50 so the tooltip sits above the world but below modals (which
sit at 100+). process_mode = ALWAYS so hovering still works during
storyteller modals. Position auto-flips to the other side of the cursor
when it would overflow the viewport.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scenes/ui/inspect_tooltip.gd.uid

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