fix(provider): Harden file/grep parsing and add LSP request timeout

[mhiro2]

Summary

• Fix file provider to correctly parse paths with :line:col suffixes (e.g., file.lua:10:5)
• Improve grep provider to handle filenames containing colons by validating candidates against the filesystem
• Add timeout mechanism to LSP multi-client requests to prevent indefinite blocking
• Add edge case tests for popup source-mode close behavior

Changes

• 2058898 fix(file): parse path line suffixes
  • Parse :line[:col] suffixes from cursor target (e.g., <cWORD> expanding to path:10:5)
  • Resolve relative paths correctly against the source buffer's directory
  • Handle Windows drive letters and absolute paths
• 96d3420 fix(grep): harden rg line parsing
  • Collect all :num:num: pattern candidates instead of assuming the first match
  • Validate each candidate path against the filesystem from last to first
  • Fallback to first candidate if none resolve to an actual file
• 281930a test(popup): cover source-mode close focus edge case
  • Add test coverage for closing the popup while in source-mode focus
• 7a5f4ed fix(lsp): add timeout for multi-client requests
  • Add configurable timeout (default 1500ms) for LSP requests across multiple clients
  • Return partial results on timeout with a warning notification
  • Prevent indefinite blocking when an LSP server is unresponsive