feat(memory): add actor and session lists

[notgitika]

This PR adds first-class actor and session list commands for AgentCore Memory.

Adds agentcore memory actor list and agentcore memory session list, with required selectors and pagination

Also adds corresponding TUI flows from the top-level Memory menu and a selected Memory's detail actions.

Reuses the actor/session picker components for the existing event flow.

Covers command behavior, direct TUI navigation, pagination, empty/retry states, and the existing event/record flows.

I did targeted memory tests command line + TUI. typecheck, lint, formatting, and bundle all pass.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.58974% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.71%. Comparing base (531d068) to head (7931b5c).

Files with missing lines	Patch %	Lines
src/handlers/memory/session/list/screen.tsx	56.09%	18 Missing ⚠️
src/handlers/memory/actor/screen.tsx	50.00%	1 Missing ⚠️
src/handlers/memory/session/screen.tsx	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1955      +/-   ##
============================================
- Coverage     96.78%   96.71%   -0.07%     
============================================
  Files           326      335       +9     
  Lines         18061    18290     +229     
============================================
+ Hits          17480    17689     +209     
- Misses          581      601      +20     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[jariy17]

Nice work! My worry is that adding actor and session to the top-level memory menu crowds it — customers still need to pick a memory first for those to be meaningful. Should it live under the selected memory rather than alongside it?