test(desktop): add edit-agent dialog e2e coverage (Phase 1B.3b-pre)

[wesbillman]

Phase 1B.3b-pre — edit-agent dialog e2e coverage

Coverage-first slice ahead of B3b (the instance-edit re-host, #centralize-personas-and-agents). Survey found EditAgentDialog had no e2e coverage past dialog-open — the readiness-screenshot spec opens it for a shot and asserts one field visible. Writing the spec against today's dialog, unmodified, off main means the B3b re-host lands guarded by a pre-existing spec rather than one written alongside the change it's meant to guard.

What it covers (3 tests, dialog's only mount path: profile panel → Edit)

1. Rename persistence — edit name → save → reopen; asserts the save survived the dialog lifecycle via the store, not local state.
2. Model round-trip — provider (Anthropic) → custom model + required credential → save → reopen; exercises the menu-based PersonaDropdownField interactions (Edit's fields are dropdown-menus, not native selects like Create's).
3. Routing pin (discovery made writing this spec) — handleEditAgent routes persona-linked agents to the definition editor (persona-dialog), never EditAgentDialog. The instance editor is reachable for persona-linked agents only via the requestOpenEditAgent event (ConfigNudgeCard side door) — no plain UI path. The test pins this routing. Consequence for B3b: the nudge-event path is the mount contract to preserve, and the inherit-pin machinery's regression net is the component-level pinning test, since no ordinary user path reaches it.

Disclosed mock boundary (spec header)

The e2eBridge update_managed_agent handler echoes name/model/systemPrompt/envVars/respondTo only — it does not model the diff-based partial-update wire semantics and ignores agentCommand/harnessOverride. This spec pins UI behavior, not wire semantics; the inherit toggle's post-save persistence is covered by B3b's component-level pinning test (inherit-toggle → gate → submit). Extending the mock alongside this spec was deliberately avoided — it would encode assumptions about the very wire semantics B3b re-hosts.

playwright.config.ts (+1 line)

testMatch is an explicit per-file allowlist in both projects — a spec absent from the list silently never runs in CI. Added to the smoke project alongside the other agent/persona specs.

Scope discipline

• Zero src/ changes. The spec passes against today's EditAgentDialog on main, unmodified — findings (the routing discovery) were reported to the channel, not fixed inline.
• Stack-independent: branches off main, no relation to the refactor(desktop): extract shared runtime/provider/model selection + env-var helpers (Phase 1B.1) #1624→feat(desktop): unified AgentDialog create entry point with create intents (Phase 1B.2) #1626→refactor(desktop): single-home the definition form as AgentDefinitionDialog (Phase 1B.3a) #1627 stack.
• Selectors introduced here become load-bearing on merge and join B3b's frozen-selector set (tracked in the plan addendum).

Verification

• 3/3 pass locally (--project=smoke), spec resolves via testMatch (--list)
• tsc, biome, file-size/px-text/pubkey guards clean
• Cross-reviewed by Pinky: independent verification of the routing finding at source, selector-set match, and his own build + smoke run (channel thread)