feat(gui): source brand marks for 23 providers that rendered a letter tile

gui/public/provider-icons/README.md

@@ -140,3 +140,85 @@ Both directions are enforced in `gui/tests/integration-marks.test.ts`, including
 luminance check that fails any single-ink near-neutral mark left as an image. That
 direction was missing until it caught `grok`; the same class of defect had already
 shipped once for `prime`, `opencode` and `kimi`.
+
+## Provider marks (2026-09-01)
+
+Sourced for the providers that were rendering a coloured initial tile. Every
+entry below was fetched from the vendor's own domain, taken from the registry's
+`baseUrl`/`dashboardUrl` rather than guessed.
+
+Published as SVG and committed with only comments, `<title>`/`<desc>` and
+`data-name` attributes stripped:
+
+- `digitalocean.svg` — `digitalocean.com` favicon, 32x32.
+- `featherless.svg` — `featherless.ai/favicon.svg`, 256x256.
+- `kilo.svg` — `kilo.ai/favicon/favicon.svg`, 32x32. Keeps its `oklch()` plate.
+- `nanogpt.svg` — `nano-gpt.com/logo.svg`, 181x187, gradient.
+- `nebius.svg` — `nebius.com/favicon/favicon.svg`, 96x96.
+- `neuralwatt.svg` — the site's Webflow-hosted brand asset, 32x32.
+- `parallel.svg` — `parallel.ai/icon.svg`, 96x96.
+- `scaleway.svg` — `scaleway.com/favicon/website/favicon.svg`, 16x16.
+- `synthetic.svg` — `synthetic.new/favicon.svg`, 54x54.
+- `zai.svg` — `z-cdn.chatglm.cn/z-ai/static/logo.svg`, 30x30.
+- `zenmux.svg` — the site's CDN-hosted brand mark, 160x160.
+
+Traced from raster, because the vendor publishes no square SVG mark. Same
+technique as `hermes-agent.svg` and `gajae-code.svg`: `potrace -s --flat` for a
+single-ink silhouette, k-means colour layers (seeded at 3, largest area first)
+for multi-colour art, downsampled to a 160px box first so the trace does not
+follow every upscaled pixel edge.
+
+- `cerebras.svg`, `novita.svg`, `siliconflow.svg`, `deepinfra.svg` — single-ink.
+- `baseten.svg`, `hyperbolic.svg`, `sambanova.svg`, `umans.svg`, `venice.svg`,
+  `vultr.svg`, `bizrouter.svg`, `orcarouter.svg` — colour-layered.
+- `nous.svg` — traced from `nousresearch.com/apple-touch-icon.png` (180x180). This
+  is the Nous Research company mark, distinct from `hermes-agent.svg`, which is
+  the Hermes product's own icon. Attributing one to the other would be wrong even
+  though the same organization ships both.
+
+Found on a docs subdomain after the vendor's marketing site offered only a
+wordmark:
+
+- `together.svg` — `docs.together.ai/favicon.svg`, 1.07:1.
+- `litellm.svg` — `docs.litellm.ai/img/logo.svg`, 1:1. The marketing site's SVGs
+  are third-party model logos, not LiteLLM's own mark.
+
+**The plate problem, recorded because the first pass shipped it.** A favicon is
+usually a glyph on a filled rounded square. Tracing luminance alone captured the
+square and produced a solid box: `baseten` came out 97.7% ink, `bizrouter` 89.3%.
+The fix reads the border ring, takes its median colour as the plate when the ring
+is uniform, and masks by distance from that colour instead of by darkness. It
+found real plates behind `baseten` (#19e76e), `cerebras` (#ef5b27), `hyperbolic`
+(#1a1a1a), `umans`/`bizrouter` (#000000) and `orcarouter` (#ffffff).
+
+### Rejected, and why
+
+- **`nousresearch.com/safari-pinned-tab.svg`** — opens with the full 512-unit
+  frame as its first path, so it renders as a black square. This is the identical
+  candidate the Hermes client mark rejected. The apple-touch-icon was used instead.
+- **LiteLLM's marketing-site SVGs** — third-party model logos, and the favicon
+  traces to a muddy blob with no legible silhouette at 19px. The docs logo was
+  used instead.
+- **Wordmarks refused** for `cerebras` (843x320 from Sanity CDN), `siliconflow`
+  (188x28), `zhipu-bigmodel` (123x25), `vultr` (218x52), `baseten` (1001x151) and
+  `chutes` (192x30). A lockup in the rail's 19px box is an illegible smear, so
+  each was replaced by a traced square mark or left to the fallback.
+
+### Still unmarked, and what was searched
+
+Six ids keep the fallback tile. Each was probed at its registry `baseUrl` and
+`dashboardUrl`, plus the vendor's docs subdomain and the conventional icon paths
+(`/favicon.svg`, `/favicon.ico`, `/apple-touch-icon.png`, `/logo.svg`, `/icon.svg`):
+
+- `chutes` — `chutes.ai` and `docs.chutes.ai` serve only the 192x30 wordmark.
+- `nscale` — `nscale.com` and `docs.nscale.com` returned no icon at any path.
+- `volcengine`, `volcengine-coding-plan`, `volcengine-agent-plan` — the Ark
+  console's SVGs are UI glyphs rather than a product mark.
+- `tencent-coding-plan` — `cloud.tencent.com` serves a 32x32 favicon whose trace
+  is unreadable at 19px.
+
+These are recorded results, not skipped work. Inventing a mark, or borrowing a
+neighbouring brand's, is a misattribution that outlives the commit.
+
+`zhipu-bigmodel` and `zhipu-bigmodel-coding` share `zai.svg`: Z.AI and BigModel
+are the same company, and the mainland console publishes only the wordmark.