Per-context view bar: swap the top-bar nav when a non-Code (Agent) context is active

[nick-pape]

Summary

Today the view bar (AppNav — Dashboard / Tasks / Personas / Root / Sessions / Knowledge / Environments / Settings) is shared across every context. Selecting a context in the left ContextNav rail is inert in Phase 0 (it only dismisses the mobile drawer), so the top-bar nav looks identical whether you're in Code or (eventually) an Agent context.

For the context → view → detail spine to make sense, the view bar must be context-scoped: when an Agent ("Claw") context is active, the top-bar should show that agent's views (overview / config / history / live), not the Code workbench tabs.

Current behavior

• ContextNav lists contexts (Code today; Fleet cluster = Coordination/Schedules above it).
• handleSelectContext (packages/web/src/App.tsx) just calls setContextNavOpen(false) — no view switch.
• AppNav renders one static tab set regardless of activeContextId.

Desired

• Selecting a context updates the active context and the view bar reflects it.
• Code → current workbench views (unchanged).
• Agent context → agent-scoped views (e.g. Overview / Config / History; later Live per Live agent view (heartbeat, autonomous sessions, continuity) #1419).
• Drives off the same data so adding contexts/agents is additive.

Scope / notes

• Presentational + routing wiring; depends on the Agent entity + context rows from Minimal Agent entity + Create Agent + agent rows in the context nav #1417 (agents must exist to have an agent context to switch into).
• Pure Phase-0 polish (Mobile ContextNav drawer reads as empty with a single context (Phase 0 polish) #1425, mobile drawer) is independent of this and can land first.

Relationship

• Part of epic GrackleCode/GrackleClaw split: the Agent entity + 2-axis context/library UX #1412 (GrackleCode/GrackleClaw split).
• Closely related to Minimal Agent entity + Create Agent + agent rows in the context nav #1417 (agent rows); this issue is specifically the view-bar swap that Minimal Agent entity + Create Agent + agent rows in the context nav #1417's scope does not call out explicitly.