[Feature] Add glm-5.3 to the z.ai coding plan catalog

[Kenmege]

Problem

z.ai has served glm-5.3 on the Z.AI Coding Plan endpoint since 2026-08-14, but Prime Agent's zai catalog tops out at glm-5.2. The registry is explicit rather than fetched (the generate-models.ts snapshot), so the model does not exist for model selection or find_models().

Evidence

• GET https://api.z.ai/api/coding/paas/v4/models with a coding-plan key lists glm-5.3 alongside glm-5.2 (created 2026-08-14).
• The models.dev zai-coding-plan catalog lists glm-5.3: 1M context / 131072 output, effort levels low/high/max, tool calls on.
• Plan docs: https://docs.z.ai/devpack/overview

Proposed change

Regenerate the snapshot (npm run generate-models in packages/ai) and scope the diff to the zai section — same shape as #1247: an 18-line addition to packages/ai/src/models.generated.ts mirroring the glm-5.2 entry (coding-plan baseUrl, zaiToolStream, thinkingFormat: "zai"; models.dev lists no per-token pricing for the plan, so cost stays 0 like its siblings).

Ready branch

Validated on Kenmege/prime-agent branch feat/zai-glm-5.3 (branched from current main, one commit, +18 lines): npm run check clean from the repo root (biome 915 files, tsgo --noEmit, installer render, browser smoke). I opened #1443 before noticing the vouching policy in CONTRIBUTING — it was auto-closed as expected for an unvouched author. Happy to re-open it, rebase, or hand the commit to a maintainer, whichever is easiest; if someone is willing to vouch, the branch is push-button ready.

[i3130002]

Hey @Kenmege

Meanwhile you can use this gist to add the model as a custom model https://gist.github.com/i3130002/95804339b51a09660c742ec12af3fc1c

[Kenmege]

Live verification on the coding plan, in case it helps the decision: with the 18-line entry applied on top of current main (06e4a19), the model shows up in discovery (find_models("glm") → zai/glm-5.3) and a real round trip through prime-agent --model zai/glm-5.3 completes normally — reasoning + tool stream behave like the other glm-5.x entries on the coding endpoint. Thanks for the gist pointer in the meantime.

[snimu]

Addressed by #1445