feat(vscode): push active editor selection to TUI via lock file

[Restodecoca]

Issue for this PR

Closes #22235

Related: #3095, #3096

Type of change

• New feature

What does this PR do?

The VS Code extension now starts a WebSocket server that pushes the active
editor file and text selection to opencode in real time, using the existing
Claude Code IDE lock file protocol. Previously, the extension only sent the
file path when the user manually invoked the "Add Filepath to Terminal"
command.

• Starts a WebSocket server on a random port when the extension activates
• Writes a lock file to ~/.claude/ide/.lock so the opencode TUI
  discovers and connects automatically
• Pushes selection_changed JSON-RPC notifications on active editor or
  text selection change
• Cleans up the lock file and closes the server on deactivation

How did you verify your code works?

• bun run check-types passes
• bun run lint passes
• Built and packaged with npx vsce package
• Installed VSIX locally, confirmed lock file created in ~/.claude/ide/
• Connected via WebSocket client, confirmed selection_changed events when
  selecting text

Screenshots / recordings

opencode.-.arquitetura-etapa-1.3-modelagem-inicial-api-poc-86agd9a2m.-.Visual.Studio.Code.2026-05-15.00-58-02.mp4

Checklist

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

[github-actions]

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

Found a potential related PR:

PR #18649: "feat: live IDE context awareness"
#18649

This PR appears related as it addresses IDE context awareness, which aligns with the goal of pushing active editor selection to the TUI. It may be addressing similar or overlapping functionality for automatically including currently open file and selected lines as context.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[Restodecoca]

Also relates to #27420 — opencode's own VS Code extension not showing file/selection context while the Claude Code extension does.

[Restodecoca]

Also related to #3472 and #7275 — these are earlier reports of the same VS Code context awareness gap (files/selection not flowing to the TUI automatically).