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

[Restodecoca]

Issue for this PR

Closes #22235
Related: #3095, #3096, #27420, #3472, #7275

Type of change

• Bug fix
• New feature

What does this PR do?

The VS Code extension's documented context awareness feature never worked because
the extension had no mechanism to push the active editor file and text selection
to the opencode TUI. This adds a WebSocket server that writes a lock file to
~/.claude/ide/.lock — the same protocol used by Claude Code and Cursor —
allowing the TUI to discover and receive real-time selection_changed events.

• Starts a WebSocket server on a random port when the extension activates
• Writes a lock file with workspaceFolders so the TUI scopes context correctly
• Pushes selection_changed notifications on active editor or text selection change
• Cleans up lock file and closes server on deactivation
• Prevents cross-project context pollution (each workspace gets its own lock file)

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
• Verified no cross-workspace context bleeding

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).

[Restodecoca]

Also worth noting: this PR prevents cross-project context pollution. Each WebSocket server writes its own lock file with the correct workspaceFolders for that VS Code window. The TUI's resolveEditorLockFile already scores lock files by workspace path match — so opencode running in project A won't pick up selections from a VS Code window opened on unrelated project B, unlike the current situation where users with only the Claude Code extension installed can see context bleeding across unrelated sessions.

Related: #26852 (stale CLAUDE_CODE_SSE_PORT can also cause cross-session contamination — our extension provides a clean, workspace-scoped lock file alternative).