Summary

• render Step interrupted as a muted interrupted note in the assistant footer instead of the red error card
• keep the footer directly below partial output with compact V1-like spacing
• intentionally use a localized message check; this PR does not change the error model, schemas, protocol, core runner, or generated clients

Verification

• bun typecheck in packages/tui
• bun test in packages/tui: 205 passed, 1 skipped
• bun x prettier --check packages/tui/src/routes/session/index.tsx
• Terminal Control at 112x34 from packages/cli against an isolated copy of the existing interruption fixture: confirmed Build · Claude Sonnet 5 · 1m 38s · interrupted, no visible Step interrupted error card, and clean Ctrl-C exit

Environment notes

• refreshed workspace links with bun install --frozen-lockfile --ignore-scripts after rebasing onto current v2
• the repository-wide pre-push Turbo typecheck was attempted but hit the host process limit while spawning tsgo (EAGAIN); the affected packages/tui typecheck passes independently
• Terminal Control text inspection passed, but PNG export still omitted terminal glyphs, so no invalid screenshot is attached