fix(tui): restore epilogue wordmark

[shuv1337]

What changed

• Reuse the canonical Shuvcode ASCII wordmark in the session epilogue.
• Add a regression test that prevents the epilogue from drifting back to the upstream OpenCode mark.

Root cause

The epilogue presentation module carried a second hardcoded copy of the upstream wordmark instead of importing the fork branding source.

Validation

• bun test test/util/presentation.test.ts test/app-lifecycle.test.tsx (4 pass)
• Full packages/tui test suite (259 pass, 1 skip)
• bun typecheck in packages/tui
• Repository push hook: 32 package typechecks