feat: add opencode plugin support

[sfc-gh-vjatania]

Summary

• Adds a native opencode plugin that routes Snowflake prompts to Cortex Code CLI, bringing opencode to parity with the existing Claude Code and Codex integrations
• New cortex_run custom tool (TypeScript, @opencode-ai/plugin) calls execute_cortex.py in --codex mode via Bun shell — reusing all existing Python router scripts unchanged
• Hybrid routing: LLM-driven via a rules file (opencode has no UserPromptSubmit hook) + a tool.execute.before hook that intercepts direct snow sql/snowsql bash calls
• bash install.sh --with-opencode installs globally to ~/.config/opencode/plugins/ and ~/.config/opencode/rules/

Files changed

File	Change
plugins/cortex-code/.opencode/plugins/snowflake-cortex.ts	New — cortex_run tool + tool.execute.before hook
plugins/cortex-code/.opencode/rules/snowflake.md	New — LLM routing rules (replaces UserPromptSubmit hook)
plugins/cortex-code/scripts/router/execute_cortex.py	Add OPENCODE env var detection → CORTEX_CODE_ENTRYPOINT="OpenCode Plugin"
install.sh	Add --with-opencode flag + install_opencode_plugin() function
tests/run-tests.sh	New "OpenCode plugin" section with 8 structural checks
plugins/cortex-code/README.md	Add opencode install instructions
README.md	Add opencode to quick-start and installer flags table

Architecture note

opencode has no pre-LLM hook equivalent to Claude Code's UserPromptSubmit, so the keyword filter cannot intercept prompts before the LLM sees them. The routing is instead:

1. Rules file (snowflake.md) — loaded globally, instructs the LLM when to call cortex_run using the same keyword set as prompt_filter.py
2. tool.execute.before hook — hard-blocks direct snow sql / snowsql bash calls, redirecting to cortex_run (hard enforcement layer)

In practice the LLM reliably routes to cortex_run given the rules file. The hook catches the edge case where it tries to use Snowflake CLI directly.

Test plan

• bash tests/run-tests.sh — all 37 structural checks pass (8 new opencode checks included)
• bash tests/run-tests.sh --unit — envelope policy + plugin unit tests pass
• Manual: bash install.sh --with-opencode → confirm files land in ~/.config/opencode/plugins/ and ~/.config/opencode/rules/
• Manual: open opencode in a project, ask "show me my Snowflake warehouses" → cortex_run is called
• Manual: attempt bash with snow sql -q "SELECT 1" → hook blocks and redirects

.... Generated with Cortex Code

[sfc-gh-ddesai]

Hi!

Thanks for your contribution. Overall it's a solid addition; opencode parity makes sense and the architecture (rules file + hook) is pragmatic given no UserPromptSubmit equivalent.

Questions / Concerns:

• Bun dependency — snowflake-cortex.ts uses Bun.$ shell syntax. Does opencode always run on Bun? If someone has opencode on Node, this breaks silently. Should document or add a Node fallback.

• Router script duplication — install.sh --with-opencode copies entire scripts/router/ to ~/.config/opencode/plugins/cortex-code-router/. Updates require re-running installer. No auto-update. Worth noting in docs.

• No functional tests for TS plugin — 8 structural checks verify files exist, but nothing tests actual cortex_run execution or hook behavior.

• Type assertion in hook — (output as { args?: { command?: string } }).args?.command is a blind cast. If opencode changes hook shapes, this silently fails.

• Version sync — PR doesn't bump version. Since v3.3.1 just landed, rebase and bump needed.

• Hook UX — tool.execute.before throws an error on direct snow sql calls. Would silent re-route (calling cortex_run internally) be better UX than erroring?

Cheers,
Dash