feat(tui): revamp responsive session dashboard

[aksOps]

Summary

• replace the sparse split-by-default view with a full-width bordered operations dashboard
• show provider, evidence-based lifecycle, session age, task, workspace, exact identity, and PR metadata
• add compact two-line selected cards and an ephemeral identity-safe live filter
• preserve Peek, dispatch, grouping, reorder, provider, store, and CLI behavior

Verification

• race detector and atomic coverage: 88.5 percent
• go vet, Staticcheck, GolangCI-Lint, Gosec, and Govulncheck
• Linux amd64 and Darwin amd64/arm64 builds
• responsive fixtures at 120x40, 80x30, 44x20, 44x12, and 44x10