Render cached agents on the console first frame

[codeaholicguy]

Summary

• seed the console agent list synchronously from a filtered, PID-live registry snapshot without awaiting adapter discovery
• mark snapshot rows as cached/unknown, preserve registered names and selection, and atomically replace or remove them when live discovery completes
• retain cached rows with visible refresh errors, preserve no-cache loading and manual retry behavior, and keep existing polling/sorting/rename/non-console paths unchanged
• document and resolve overlap with the responsiveness work already merged in perf(cli): memoize console preview rows #156-refactor(cli): split console state contexts #158

Validation

• npm test --workspace @ai-devkit/agent-manager -- --maxWorkers=1 — 504/504
• npm test --workspace packages/cli — 974/974
• agent-manager lint, typecheck, and build — passed
• CLI lint — 0 errors (5 pre-existing warnings); build — passed
• npx ai-devkit@latest lint --feature console-fast-initial-state — passed

Risks / overlap

The branch is rebased onto current main, including #156-#158. The resolution preserves split agent/channel contexts and preview memoization; cached metadata is confined to the agent context. No schema, dependency, polling cadence, or listAgents() behavior changes are included.