feat(desktop): calmer, more realistic pet roam + split roam modules

[OutThisLife]

Summary

The floating desktop pet wandered almost constantly — it works, but it never sat still. Two causes: every idle beat picked a new walk, and hops fired ~45% of the time. The result read as nervous, not alive. This makes movement the exception, not the default, and splits the overgrown roam hook into focused modules.

Behavior — calmer & more realistic

Grounded in ambient game-AI practice (GameAIPro ch.36 "Breathing Life into Your Background Characters" + standard idle/wander state machines, where idle dwell times are modeled as exponential/memoryless):

• Loaf, don't pace. Most decision beats now just keep resting (REST_CHANCE = 0.62) instead of always re-walking.
• Memoryless dwell times. Pauses draw from an exponential distribution (mostly short rests, the occasional long loaf) instead of a uniform 1.8–5.2s window, so the cadence never reads as a metronome.
• Fewer hops. Hop chance dialed back 0.45 → 0.2 (hopping is the jumpiest, noisiest motion).

Net effect: the pet still strolls, hops, and falls exactly as before — just far less often, with natural variation between bouts.

Structure — no god-file

The 459-line use-pet-roam.ts mixed DOM surface measurement, behavior decisions, and the physics loop. Per the repo TS style ("a hook should own one narrow job; prefer colocated modules over god hooks") it's now three focused files:

• roam-behavior.ts — what to do & when: dwellMs, chooseMove, pickStrollTarget + tuning constants. Pure, rng-injectable.
• roam-geometry.ts — where it can stand: snapshotLedges, overlayLedge, resolveLedge, overlapsX, groundTop. DOM measurement + pure ledge math.
• use-pet-roam.ts — the physics/RAF loop only.

Tests

Deterministic, rng-seeded unit coverage for the decision + geometry helpers — behavior contracts (clamping, rest-bias majority, ledge resolution), not snapshots. apps/desktop vitest: 25 passed.

Test plan

• vitest run on the new + existing pet tests — 25 passed
• tsc -p . --noEmit — clean
• eslint on all touched files — clean
• Manual: enable pet roam in the desktop app and confirm it loafs in place most of the time, with occasional strolls/hops, and still falls/settles correctly across the composer, profile rail, status bar, and route overlays.