fix(tui): guard Object.entries against null MCP/theme/input

[pantha704]

Issue for this PR

Closes#44100

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

TUI dies with TypeError: Object.entries requires that input parameter not be null or undefined on 0.0.0-beta-17823 (same stack as #44100). Solid is iterating a value that is still null: theme colors, MCP status, tool input, attention sounds.

This PR passes ?? {} (or optional chaining) at those call sites, falls back to the built-in opencode theme if the active one is missing, and adds a test that resolveTheme({}) does not throw.

How did you verify your code works?

Added packages/tui/test/theme.test.ts coverage for a theme object with no theme key.

Screenshots / recordings

N/A (crash guard, no UI change).

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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[Enough1122]

AI code review — automated review for reference, author can ignore or act on any point.

Low-risk hardening, but I'd push back on the approach: most of these guards defend an invariant that the codebase already enforces, and scattering ?? {} across consumers is the weaker fix compared to enforcing it at one place.

1. sync.data.mcp should never be null today. The TUI store types it as a non-optional record (packages/tui/src/context/sync.tsx:166-174), initializes it to {} (sync.tsx:217), and every writer already normalizes server payloads (setStore("mcp", reconcile(x.data ?? {})) at sync.tsx:918; same for lsp at :737/:915). So what concrete runtime path produced undefined/null here? If you have a crash trace, the durable fix is at that write site (or make the type honest — mcp?: Record<...> — so tsc enumerates every consumer instead of manual auditing). Without a repro, ~20 call-site guards add noise and will drift: e.g. packages/tui/src/routes/session/footer.tsx:15 still calls Object.keys(sync.data.lsp) unguarded two lines below the newly-guarded mcp memos, and dialog-mcp.tsx stays guard-free by design.

2. The one behavioral change deserves its own note.packages/tui/src/context/theme.tsx:266 falling back to DEFAULT_THEMES.opencode silently masks a missing/corrupted built-in theme entry instead of failing loudly; acceptable, but worth a comment since every other hunk is a pure no-op guard.

3. Test scope (packages/tui/test/theme.test.ts:38-42): good start; also assert a color resolves from defs/fallbacks (e.g. background), since thinkingOpacity alone passes even if color resolution regressed.

Happy with #2/#3 as-is; #1 needs either a repro or a narrower scope before this lands.