T-15: Terminal session isolation between windows (diagnostic + fix)

[kirich1409]

Part of EPIC #193. Depends on #201.

Description

Diagnose whether terminal sessions leak across windows. Test: open two windows with different projects, create an agent session in each, verify AgentOrchestratorFeature.State.sessions in window A shows only its own sessions. If the diagnostic fails, scope sharedTerminalRegistry — add a windowID to TerminalSession and filter in AgentOrchestratorFeature by the owning window.

Acceptance Criteria

• Integration test: two windows, two sessions — window A sees only its sessions; window B sees only its own
• sharedTerminalRegistry.allSessions enumeration works without crash under multi-window
• If a fix is required, TerminalSession is extended with windowID without breaking external APIs

Module / Layer

AgentOrchestrator / TerminalFeature + sharedTerminalRegistry

Complexity

Medium (up to Large if a scope fix is required)

Notes

Research-recommended task — diagnostic work precedes any implementation decision.