fix: validate prompt history/stash entries to prevent JSON display bug

[Ashwinhegde19]

Summary

Fixes a bug where corrupted prompt history/stash entries with non-string input fields would display as JSON in the input box.

Problem

When prompt-history.jsonl or prompt-stash.jsonl files get corrupted, entries with non-string input fields (objects, arrays, numbers) would pass through the filter and display as [object Object] or JSON text in the input box, preventing users from typing or reverting messages.

Solution

Added runtime validation to filter functions in both history.tsx and stash.tsx:

history.tsx:

.filter((line): line is PromptInfo => {
  return line !== null && typeof line === "object" && typeof line.input === "string" && Array.isArray(line.parts)
})

stash.tsx:

.filter((line): line is StashEntry => {
  return line !== null && typeof line === "object" && typeof line.input === "string" && Array.isArray(line.parts) && typeof line.timestamp === "number"
})

Testing

• Added comprehensive test file test/cli/tui/prompt-corruption.test.ts with 5 test cases
• Tests cover validation logic, edge cases, and file operations
• All tests pass: bun test test/cli/tui/prompt-corruption.test.ts

Self-Healing

The existing self-healing behavior is preserved - corrupted files are automatically rewritten with only valid entries after loading.

Fixes #12151

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[Ashwinhegde19]

Note on Test Failure:

The CI test failure is in @opencode-ai/app#test (Playwright E2E tests), which is unrelated to this PR.

Details:

• ✅ Our new test passes: packages/opencode/test/cli/tui/prompt-corruption.test.ts (5/5 tests pass locally)
• ❌ Failure is in packages/app Playwright E2E tests - a pre-existing CI flakiness issue
• 📁 This PR only modifies files in packages/opencode (history.tsx, stash.tsx, test file)

The app package's E2E tests are known to be flaky in CI. This is a separate issue from the prompt corruption bug fix.

[github-actions]

Closing this pull request because it has had no updates for more than 60 days. If you plan to continue working on it, feel free to reopen or open a new PR.