fix(logging): suppress cursor-sdk shell-parser tree-sitter warn from TUI

[justin-carper]

Problem

@cursor/sdk's bundled shell-parser emits a one-shot console.warn:

shell-parser: tree-sitter natives are unavailable in this artifact; shell command analysis degrades to parsingFailed

This fires when the SDK's vendored tree-sitter natives fail to load (e.g. when opencode runs the plugin under Bun). opencode renders plugin stderr into the TUI prompt, so the line appeared visually in the prompt even though it is benign — shell command analysis simply degrades to parsingFailed, which the SDK handles.

The repo already intercepts the SDK's console.log rules/skills load diagnostics and routes them to opencode logging; console.warn was never covered.

Fix

Extends the existing interceptor pattern to console.warn on both transports:

• In-process (src/provider/cursor-log-intercept.ts): installCursorLogInterceptor now wraps console.warn; known SDK warning prefixes are routed through pluginLog("warn") (opencode app.log) instead of reaching stderr. Everything else passes through unchanged.
• Sidecar (src/sidecar/agent-host.mjs): the Node child gets the same wrapper; matched lines are forwarded as {ev:"log", level:"warn"} over the existing JSONL protocol, so nothing hits child stderr.

The message remains visible in opencode logs (service opencode-cursor, level warn) — just not in the prompt.

Tests

• test/cursor-log-intercept.test.ts: exact shell-parser line routes to client.app.log with level warn; unrelated warns pass through the original.
• test/sidecar.test.ts + test/fixtures/fake-cursor-sdk.mjs: new emitShellParserWarn fixture option; asserts the sidecar forwards the warn via onLog and drops unrelated warns.

Verification

• npx tsc --noEmit — clean
• npm test — 616/616 pass