feat(workflow): pick one model per Workflow (not a static 「Each Bot's own model」) #1502

Written-by: bot-im
Owner: Dev

Ask

Owner (2026-10-28 Asia/Shanghai): 「workflow要能选模型」 — Workflow must let you choose a model, not only show a static label.

What happens today

• Graph data already has node.model (define_workflow / README; plugins/workflow/src/{graph,service,ephemeral}.js pass it into the ephemeral Bot as model: node.model || seated?.model).
• The product UI never lets you set it:
  • Stage Details shows a hard-coded 「Model → Each Bot's own model」 / 「跟随各个 Bot 的模型」 (plugins/workflow/client.js Details).
  • Settings → Workflow graphs node inspector edits prompt / role / tools only — no Model field.
  • Stage flowchart edit inspector is prompt-only.

So a run always inherits whatever the seated Bot (or host default) carries; there is no Workflow-side control.

Expected

1. Per-node Model control in edit mode on both surfaces that already edit nodes:
   • Settings → Workflow graphs inspector
   • Stage / flowchart node inspector (when editing)
2. Options come from the same model catalog the rest of FlyBot uses (Harness / roster.models / existing model-menu patterns in core/src/client/model-menu.js). Do not invent a parallel list.
3. Empty / default keeps today's behavior: ephemeral Bot uses seated Bot model, else host default (nodeConfig already does node.model || seated?.model).
4. Choosing a model writes node.model through the existing workflow/graph (or equivalent) save path and survives reload.
5. Details / summary copy should show the chosen model (or 「Each Bot's own model」 only when unset) — not a forever-static string.
6. ZH/EN strings via existing tr(); changelog fragment; plugins/workflow tests cover pick → save → state round-trip; no hand-edited core/client.js (regenerate with repo scripts if core is touched).

Out of scope

• Do not change pause/resume/stop, ephemeral hide-from-sidebar, or real-run gating.
• Do not require a workflow-level single model unless you find the data model already needs it; per-node is the ask (matches stored node.model).
• Leave HugoXK-claimed work (fix(workflow): dark themes lose the flowchart node role sub-label to a hardcoded grey (#1484 regression) #1495 / policy: please do not pick up a FlyBot issue that has no PR yet, unless the FlyBot team posts pickup-ok #1496 pickup-ok) alone.

Prod note

Fleet is already on tip 55e1c27a (Deployment upgrade after owner 「升级一下」). Still: do not ask for another prod upgrade in this PR's body; owner decides after merge.

Acceptance

• Edit a node → pick a model from the catalog → save → workflow/state (or graph read) shows that model on the node.
• Clear / leave empty → run still starts; ephemeral uses seated/default as today.
• A run with an explicit node.model spawns the ephemeral Bot with that model (assert in unit test around nodeConfig / spawn stub).
• Details no longer always say only 「Each Bot's own model」 when a node has a model set.