fix: properly encode file URLs with special characters

[yudgnahk]

Summary

Fixes critical bug where filenames containing special characters (#, ?, %, spaces) caused ENOENT errors and path truncation throughout the application.

Root Cause

Using string interpolation `file://${path}` instead of proper URL encoding. The # character is treated as a URL fragment identifier, causing paths like /path/to/file#name.txt to be truncated to /path/to/file.

Solution

• Backend (Node.js/Bun): Use pathToFileURL() and fileURLToPath() built-in APIs
• Frontend (Browser): Custom encoding/decoding helpers (Bun APIs not available in browser)
• Special characters are now properly encoded: # → %23, ? → %3F, etc.

Changes

Backend Files (7 files)

• packages/opencode/src/session/prompt.ts - Fixed 2 occurrences
• packages/opencode/src/cli/cmd/run.ts - Fixed 1 occurrence
• packages/opencode/src/acp/agent.ts - Fixed 4 occurrences
• packages/opencode/src/lsp/index.ts - Fixed decoding with fileURLToPath()
• packages/opencode/src/cli/cmd/tui/component/dialog-status.tsx - Fixed 1 occurrence
• packages/opencode/src/cli/cmd/tui/component/prompt/autocomplete.tsx - Fixed 1 occurrence
• packages/opencode/test/session/prompt-special-chars.test.ts - Added test case for # character

Frontend Files (2 files)

• packages/app/src/components/prompt-input.tsx - Custom pathToFileUrl() helper
• packages/app/src/context/file.tsx - encodeFilePath() and decodeFilePath() helpers

SDK/Demo Files (2 files)

• packages/sdk/js/example/example.ts - Fixed example code
• packages/app/src/components/file-tree.tsx - Fixed drag-and-drop encoding

Testing

✅ All tests pass: bun test - 884 pass, 1 skip, 0 fail
✅ TypeScript clean: All packages typecheck successfully
✅ Real file testing: Created test files file#name.txt, file?name.txt and verified operations
✅ Backward compatible: Normal paths produce identical output

Impact

Fixes:

• File tagging with @file#name.txt
• Diff/Review view loading
• Drag-and-drop operations
• SDK file operations
• Write tool for files with special characters

11 files changed, 114 insertions(+), 21 deletions(-)

Related Issues

Fixes #11790
Partially fixes #9804
May improve #9173, #8172, #8759, #11630

[github-actions]

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

I found 1 potentially related PR:

Related PR:

• fix(tui): Handle file paths with hashtags #11870 - fix(tui): Handle file paths with hashtags
  • Related because it addresses handling file paths with special characters (hashtags), which overlaps with the core issue in PR fix: properly encode file URLs with special characters #12424 about encoding file URLs with special characters like #. This appears to be a more targeted fix for the TUI component, whereas fix: properly encode file URLs with special characters #12424 is a comprehensive fix across multiple backend and frontend files.

The other match (#10049 about Windows drive letter case) is less directly related to special character encoding.