fix(loops): source model picker from per-adapter task catalog

[charlesvien]

Problem

GLM-5.2 shows up in the main create-task model picker but not in loops.

Changes

• LoopModelFields now builds its model list from the same per-adapter agent.getPreviewConfigOptions source as the main create-task picker: curated models, friendly labels, GLM-5.2 behind the existing posthog-code-glm-model flag, plan-restricted models dropped and a pinned model on an existing loop always kept selectable.
• New loopModels.ts constrains reasoning-effort options to the effective model's supported set (GLM offers Auto/High/Max) and clamps invalid combos when the adapter or model changes, so the form can no longer submit anything the server's validation in process_task/utils.py rejects.
• Loop detail and the review step now show the real loop default ("Claude Sonnet 5 (default)") instead of the gateway session default. LOOP_DEFAULT_MODELS mirrors the backend's DEFAULT_MODEL_BY_RUNTIME_ADAPTER unchanged: claude stays on claude-sonnet-5, codex on gpt-5.

How did you test this?

• 21 new parameterized unit tests in loopModels.test.ts (option building, GLM flag gating, per-model effort sets, clamping).
• Full @posthog/ui suite (2063 tests), @posthog/ui and @posthog/web typechecks and Biome all pass.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[trunk-io]

😎 This pull request was merged.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 83efe25.}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/ui/src/features/loops/hooks/useLoopModelConfigOptions.ts:30
**Catalog failures remove model choices**

When the preview-config request is pending or fails, this hook returns an empty catalog, causing the loop picker to show only “Default (recommended)” with no loading or error indication instead of retaining the previous fallback model choices.

_{Reviews (1): Last reviewed commit: "source loops model picker from preview c..." | Re-trigger Greptile}

[github-actions]

Frontend-only fix to the loops model picker reusing existing, already-tested infra (preview config catalog, restricted-model filtering, reasoning-effort helpers); all real behavior enforcement stays server-side. The one Greptile P1 concern (empty catalog on load/error) is in fact addressed by the code's fallback-model-options path, matches its [resolved] status, and 21 new parameterized tests cover the new logic directly.

• Author wrote 61% of the modified lines and has 8 merged PRs in these paths (familiarity MODERATE).
• 👍 on the PR from greptile-apps[bot].

Gate mechanics and policy version

Gate		Result
prerequisites	✓	all clear
deny-list	✓	no deny categories matched
size	✓	301L, 6F substantive, 568L/7F incl. docs/generated/snapshots — within ceiling
tier	✓	T1-agent / T1d-complex (568L, 7F, single-area, fix)
stamphog 2.0.0b3		.stamphog/policy.yml @ 3792cce · reviewed head 83efe25