Visual: add procedural biome grass and wind

[ael-dev3]

Scope and branch boundary

• Base: main at 3ca99d2d263453fbb112a7a21fa1bfde294e186b (Alpha 0.3.8).
• Head: 341cecb89032e42f62e806f0e8394ba2147833dc.
• This is a visual-only grass/wind layer. It does not include, modify, merge, or depend on historical resource PRs Alpha 0.3.7: add Genesis resources and compact Realm chrome #48/Alpha 0.3.7: stage Gold Mine candidates and inspection art #49, draft Alpha 0.3.9: Gold Mine wagon expeditions #51 (Gold Mine wagon expeditions), its stacked Alpha 0.3.9: Canonical Genesis forest layout #52 (canonical forest layout), or draft Harden profiled founder admission and castle ownership #54 (founder admission/castle ownership).
• Alpha 0.3.9: Gold Mine wagon expeditions #51/Alpha 0.3.9: Canonical Genesis forest layout #52 share future Realm-scene integration surface only; if either lands first, reconcile that one integration file deliberately against landed main. No current PR is merged or retargeted here.
• The reviewed 10,000-cell Genesis world is already present on this base, so this PR uses that canonical surface directly rather than adding a synthetic production-adjacent fixture.

What changed

• Replaced the sparse CPU-matrix-animated green-tuft / dry-tuft path with deterministic procedural, low-poly instanced grass; static stones remain a separate bounded detail family.
• Added renderer-neutral macro/meso value noise, deterministic stratified scatter, biome profiles, complete bare patches, terrain tinting, slope thinning, placement clearance, permanent castle-slot suppression, and generic feature-root exclusion circles.
• Added camera-local active windows, LRU cell data, deterministic rank thinning, fixed-capacity instance pools, opaque edge shrink/fade, and per-quality hard ceilings.
• Added a MeshStandardMaterial.onBeforeCompile GPU-wind path pinned to the Three r185 shader hook with a stable cache key, fail-closed contract fallback, planted root flex, max-sway bounds, and no grass raycasting.
• Added selected-cell (42%) and hovered-cell (70%) shader flattening; ordinary motion interpolates uniforms and reduced motion settles immediately.
• Replaced the 180 ms CPU wind timer with a demand-driven, rAF-aligned scheduler: High 24 fps, Balanced 16 fps, Reduced static; overview, hidden tabs, reduced motion, and disposal stop animation.
• Added bounded grass telemetry, including terrain-kind counts, without individual positions or player data.

Biome policy

Biome	High candidates/cell	Complete-bare threshold
Meadow	30	0.12
Lowland	24	0.20
Forest	20	0.32
Heath	14	0.47
Ridge	4	0.84
Ancient Stone	2	0.96
Lake	0	1.00
Render apron	5	0.65

Balanced uses 0.62x candidate density and Reduced uses 0.25x, with deterministic rounding.

Fixed runtime ceilings

Quality	Active clumps	Triangles	Draws	Radius	Wind
High	<=14,000	<=210,000	1	12 cells	24 fps
Balanced	<=7,000	<=84,000	1	9 cells	16 fps
Reduced	<=2,000	<=18,000	1	6 cells	static

Wind updates material uniforms only. Focused regression coverage proves no setMatrixAt or instanceMatrix.needsUpdate work occurs during wind steps; matrices update only on active-window repack.

Canonical 10,000-cell evidence

The new canonical-surface test runs against 10,000 playable / 10,981 rendered cells. At the center High keep window it attests:

• 469 active candidate cells; 397 cached cells; 1,880 packed clumps; 28,200 grass triangles; one draw call.
• presentation digest (packed matrices + phases): d096966756353ad1d09c90c68ef51a23a6348dc8b8105b638a47a624844401c3.
• overview has zero detailed grass; traversal stays below the 2,048-cell cache and all High allocation ceilings.

Verification

Passed:

• tsc -b
• full Vitest: 153 files / 1,504 tests
• ordinary production build, runtime-asset and Gold Mine candidate verification, production-output exclusions
• file-size and license policy verification
• canonical Pages-style build and Pages configuration validation with shared alpha disabled
• focused deterministic noise/generation, geometry, shader, active-window, layer, lifecycle, scheduler, and canonical-Genesis tests

Not completed locally:

• rendered WebGL browser QA failed closed before launch because the required local authorized castle source archive is unavailable; no screenshots/video are claimed.
• production alpha attestation could not reach https://warpkeep.com from this environment.
• CodeQL and dependency-audit binaries are not installed locally; hosted CI remains the authoritative gate.

Non-goals and residual risks

No SpacetimeDB schema/binding/reducer change, gameplay authority/resource/collision/pathfinding change, deploy, Pages publish, backend publish, tag, release/version claim, or merge occurred.

Density and color remain provisional art-direction values; browser thermal behavior needs continued observation. Grass is decorative and does not react physically to units. Future reviewed structures must supply generic exclusion circles. The shader hook remains intentionally coupled to pinned Three r185, and full-Realm overview intentionally omits individual grass.

[ael-dev3]

Superseded by the audited Alpha 0.3.11 integration in #64, now merged to protected main. Accepted work was reconciled, corrected where needed, and validated there; this original branch is intentionally not merged again.