Render continuously and optimize the glTF viewer

Remove vsync and dirty-flag frame gating, optimize PBR sampling and lighting, add a direct-to-canvas loadout, and preserve camera state on viewer resize.

Add regression coverage and update rendering documentation.

Amp-Thread-ID: https://ampcode.com/threads/T-01a0b382-1e79-712b-abd1-d29201c9bb5e
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

coredocs/reference/errors.md

@@ -60,16 +60,16 @@ On row growth, consume the returned descriptor before the next access and commit
 | `GRAPH_BLEND`, `GRAPH_WRITE_MASK` | Invalid fragment blend or write-mask bits. |
 | `GRAPH_SAMPLER` | Invalid sampler enum/compare value. |
 | `GRAPH_LOAD_OP`, `GRAPH_STORE_OP` | Attachment operation is not allowed. |
-| `SURFACE` | Surface acquisition/recovery failed; core marks the SAB dirty to retry later. |
+| `SURFACE` | Surface acquisition/recovery failed; the continuous render loop retries later. |
 
 Shader compilation, bind-layout mismatch, device limits, invalid upload extents/mips, and WebGPU validation are not all normalized to these codes. Validate graph inputs before switching and retain the previous graph source for recovery.
 
 ## Safe state transitions
 
 1. Initialize once and cache descriptors.
-2. Create rows, allocate IDs, and initialize complete rows before publishing `sabDirty`.
+2. Create rows, allocate IDs, and initialize complete rows. Pause first if an update must not overlap rendering.
 3. Compile graphs before switching. Compilation stores a graph but does not validate every GPU-dependent property; activation can still fail.
 4. For bundle-invalidating mutation, set `bundleDirty` first. Leave it set after compile/switch failure, because that intentionally suppresses stale rendering. Repair and switch successfully; never clear it merely to hide an error.
 5. Upload textures with transfer ownership. Delete cached sources when no future loadout needs them.
-6. Pause when editor state should stop timing/render-loop progress. `pause` does not cancel requests or clear dirty lanes.
+6. Pause when editor state should stop timing/render-loop progress. `pause` does not cancel requests or clear control lanes.
 7. On worker failure, reject all pending requests and rebuild the entire worker/canvas/core state. Requests are not generally safe to replay because create, allocate, delete, switch, and texture operations may already have committed.

coredocs/reference/worker.md

@@ -7,18 +7,18 @@ All fields below are top-level beside `type` and `request`. Except for `init` an
 | `init` | `canvas: OffscreenCanvas`, `arenaBytes: number` | `[canvas]` | `{ buffer: SharedArrayBuffer, rows: Descriptor[], features: string[] }` | Once only; initializes WASM/WebGPU. `features` lists optional device features that were available (`timestamp-query`, `indirect-first-instance`). |
 | `create-rows` | `name`, `rows`, `stride`, `format` | — | `{ rows: descriptor, commit: boolean }` | Nonempty name; rows > 0; stride ≥16 and multiple of 16; format f32/u32/i32. Existing name may only retain format/stride and grow. `commit: true` means the rows moved: copy the old bytes into the descriptor and send `commit-rows`. |
 | `create-rows-batch` | `rows: Array<{name,rows,stride,format}>` | — | `{ rows: descriptor[] (input order), commit: string[] }` | Nonempty. Sequential; in-place creations/growths survive a later failure, staged relocations are discarded. `commit` lists the arrays that moved. Active GPU resources refresh once for in-place growth. |
-| `commit-rows` | `names: string[]` | — | `undefined` | Publishes staged relocations after the caller copied them. Must name every staged array. Frees the old rows, refreshes bound GPU buffers once, sets `sabDirty`. While a relocation is staged the worker queues every other request until this arrives. |
+| `commit-rows` | `names: string[]` | — | `undefined` | Publishes staged relocations after the caller copied them. Must name every staged array. Frees the old rows and refreshes bound GPU buffers once. While a relocation is staged the worker queues every other request until this arrives. |
 | `delete-rows` | `name` | — | `undefined` | Not `signals`, not active slots, not referenced by active graph. |
 | `allocate-object` | `name`, `count: u32 = 1` | — | `{ id, rows: descriptor, commit: boolean }` | Not `signals`; `count` > 0; reserves `count` contiguous rows starting at `id`; may grow. `commit` as in `create-rows`. |
 | `delete-object` | `name`, `id: u32` | — | `undefined` | ID must be the first row of an active span; the whole span is zeroed. |
-| `sync-rows` | `name`, `first: u32 = 0`, `count: u32` | — | `undefined` | Uploads rows `first .. first + count` of the array into every active GPU buffer bound to it (any `sync`) and sets `sabDirty`. `ROW_RANGE` when the span exceeds the array. No-op without an active loadout. |
+| `sync-rows` | `name`, `first: u32 = 0`, `count: u32` | — | `undefined` | Uploads rows `first .. first + count` of the array into every active GPU buffer bound to it (any `sync`). `ROW_RANGE` when the span exceeds the array. No-op without an active loadout. |
 | `compile-graph` | `serialized: string` | — | graph ID string | Parses and stores; same ID replaces previously stored graph. Does not activate it. |
-| `switch-loadout` | `id` | — | `undefined` | Builds GPU resources and activates stored graph. Clears `bundleDirty`, sets `sabDirty`. |
-| `upload-texture` | `name`, `mipLevel: u32`, `image: ImageBitmap` | `[image]` | `undefined` | Uploads immediately if active graph has the texture and caches source for future switches. Source extent must fit destination/mip. Sets dirty. |
-| `delete-texture` | `name` | — | `undefined` | Deletes/closes cached mip sources; does not remove graph texture or mark dirty. |
+| `switch-loadout` | `id` | — | `undefined` | Builds GPU resources and activates stored graph. Clears `bundleDirty`. |
+| `upload-texture` | `name`, `mipLevel: u32`, `image: ImageBitmap` | `[image]` | `undefined` | Uploads immediately if active graph has the texture and caches source for future switches. Source extent must fit destination/mip. |
+| `delete-texture` | `name` | — | `undefined` | Deletes/closes cached mip sources; does not remove graph texture. |
 | `play` | — | — | `undefined` | Enables render-loop ticks; resets last-time baseline. |
 | `pause` | — | — | `undefined` | Stops loop updates/renders. |
-| `set-fps` | `fps: u32` | — | `undefined` | 0 uncapped; maximum 1000. Does not itself dirty a frame. |
+| `set-fps` | `fps: u32` | — | `undefined` | 0 uncapped; maximum 1000. |
 | `set-profiler` | `enabled` (boolean-coerced) | — | boolean | Result says timestamp queries are supported. Enables only when requested and supported. |
 
 Rust/WASM numeric conversion applies to `u32` fields; callers should send finite nonnegative integers in range rather than rely on coercion.
@@ -41,6 +41,8 @@ When enabled and supported, the worker polls every 250 ms and may send an unsoli
 }
 ```
 
+`milliseconds` is the sum of GPU timestamp durations across passes, not CPU frame time or the interval between frames. It excludes scheduling waits and readback latency; `readbackMilliseconds` reports the time from starting that frame to receiving its timestamp results.
+
 One pass timing corresponds to a compiled execution; compatible adjacent render passes are merged into one execution labelled `first … last (N draws)`. Samples are throttled and asynchronous, so they are diagnostics, not one event per frame. Disabling clears pending published statistics and the worker polling interval.
 
 ## Texture lifecycle