feat(tui): hint to view workflow agents after workflow tool runs

[wqymi]

Summary

• Dynamic-workflow agents already register as subagents in the session and appear in the Subagents panel, but nothing told users the shortcut to view them existed.
• Render the session_child_first keybind hint after workflow tool messages too, with workflow-specific copy (view workflow agents), reusing the existing panel and navigation.

Why

Workflow guest scripts spawn agents via agent()/parallel()/pipeline(), all using actor.spawn({ mode: "subagent", sessionID }) against the main session — so they are already listed in DialogSubagent and drillable to their transcripts. The only gap was discoverability: the actor tool advertises the panel with a view subagents hint, but the workflow tool rendered none.

Change

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx (AssistantMessage):

• Add hasActorPart / hasWorkflowPart memos.
• Show the keybind hint when a message has an actor or workflow tool part.
• Copy is view workflow agents for workflow messages, view subagents otherwise (mixed messages fall back to the subagent wording). Same session_child_first keybind — moveFirstChild() already includes workflow agents.

No new data plumbing, schema, persistence, or runtime changes.

Verification

• Design spec lives in the internal docs repo (docs/compose/specs/2026-06-25-workflow-agents-view-hint-design.md).
• Note: bun typecheck could not be run in the authoring sandbox (missing installed deps). The change is a refactor of an already-type-checked props.parts.some(...) expression plus a string ternary, so it introduces no new types. Please confirm bun typecheck from packages/opencode in CI/your env.
• Manual: run a workflow in the TUI; confirm the view workflow agents hint renders after the workflow tool message and the shortcut opens the Subagents panel listing the workflow's agents.

Note on diff

The chore: add generated files commit (regenerated SDK types.gen.ts) was already part of this branch's history prior to this work; the functional change here is the ~12-line index.tsx edit.