Add unit coverage for the template launch dialog

[selfcontained]

Summary

• LaunchTemplateDialog (automations-launch-dialog.tsx) had zero direct coverage despite owning the template launch contract and being the second consumer of the useStartupAttachments hook extracted in Extract shared useStartupAttachments hook #876 (the first consumer path is pinned via use-create-agent-form.test.tsx).
• Adds 13 jsdom tests that render the real dialog, the real useTemplateActions mutation, and the real ContextPicker, mocking only the HTTP seam (@/lib/api) and the toast sink — so the whole chain from form state to wire payload is pinned end to end.

What's pinned

• Required-arg gating (blank + whitespace) including the Enter-key submit path that bypasses the disabled button, with a microtask flush so the no-call assertion observes settled state
• Optional args never block launching; typed args sent keyed by lowercased name, untouched ones omitted
• Agent-type override via the combobox reaches the payload
• JSON branch: exact body (agentType only for no-arg templates; no stray args/startup fields)
• Multipart branch: dropped files (deduped across drops), popover-added links, args, and agentType all land in FormData; removed files stay out; absent fields are absent, not serialized empties
• Success closes the dialog and navigates to the new agent (asserted via real router location); failure toasts and stays open; resubmits while pending are suppressed (asserted after settle)
• Terminal templates hide the agent-type select and media affordances; allowMedia: false ignores drops; drop zone arms only for file drags

Verification

• 12-mutant battery against the dialog + launchTemplate mutation — all killed (one submit-gate mutant initially survived a too-early assertion; fixed by asserting post-settle)
• One general review round: 0 must-fix; 1 should-fix + 2 nits applied (microtask flush, positive control for empty-state copy, pin POST method)
• pnpm run check, full unit suites (web 617→630), pnpm run finalize:web, inert E2E 175 passed, live lane 11 passed

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