Add live subagents and context controls

[Suren878]

Summary

• Add live Terminal subagent cards for delegate_task and spawn_subagent with Matrix-style codenames, expansion, previews, and terminal states.
• Add queued busy input handling plus richer model/subagent status text in the TUI.
• Add context clear/compact markers, corrected effective-context token estimates, and context status tests.
• Refactor picker/voice runtime pieces and add README release highlights for the upcoming release.

Test Plan

• go test -count=1 ./...
• go vet ./...
• go build ./...
• git diff --check
• /root/go/bin/golangci-lint run --new-from-rev=origin/main ./...