Add OpenCode 2 beta adapter

[shanebishop1]

Adds an isolated OpenCode 2 beta package while keeping the existing V1 package and release line unchanged.

What changed

• Added opencode-command-hooks-v2@0.1.0-beta.0, pinned to @opencode-ai/plugin@0.0.0-next-15853.
• Added the V2 Promise adapter for tool before/after hooks, synthetic injection, event dedupe, and cleanup.
• Mapped compatibility and durable execution lifecycle events to the existing session.start and session.idle hooks.
• Normalized V2 subagent/agent events to the existing task/subagent_type config contract.
• Refactored shared execution behind host injection/toast ports and passed project directories explicitly through config discovery, agent loading, and shell execution. V1 remains on its existing SDK adapter.
• Added a one-time diagnostic for unsupported V2 server-plugin toasts and uses resume: false for synthetic messages to avoid unsolicited turns.
• Added unit, regression, package, and real-host E2E coverage, plus separate V1/V2 build outputs.
• Added PR CI and a V2 release workflow. Both run the packed package against the pinned OpenCode 2 host.
• Updated the README and impact report with compatibility, rollout, and rollback details.

Why

OpenCode 2 does not load V1 plugin exports and runs as a long-lived multi-location service. A separate package avoids breaking V1 users, while the shared host-neutral core prevents the adapters from drifting. Resolving each session through the V2 client provides the correct project directory instead of relying on process cwd.

Real-host verification

The E2E installs the packed V2 package and @opencode-ai/cli@0.0.0-next-15853 into a temporary project, starts a private server on an OS-selected port, and polls until plugin activation completes. Temporary HOME/XDG paths and explicit test credentials keep it separate from the normal opencode installation and service. The test passes and confirms opencode-command-hooks.v2 completes setup in the real host.

Verification

• npm run lint
• npm run typecheck
• bun test: 143 passed
• OPENCODE2_E2E=1 bun test tests/e2e.v2.test.ts: passed twice consecutively
• bun run build:all
• V1 and V2 npm pack --dry-run: passed
• Workflow YAML parsing: passed

OpenCode 2 remains beta. Server plugins still cannot display TUI toasts, and exact CLI/plugin version pins remain required.

Issue #5: active subagent waits

• Added opt-in excludeSubagentWait support for session.idle hooks in both adapters.
• V1 tracks task calls; V2 normalizes native subagent calls to the same lifecycle.
• Only opted-in hooks are suppressed, and they resume after all active calls complete.
• Session deletion clears stale tracking state.
• The earlier sessionScope approach was fully reverted because it did not address active subagents.

Verification: npm run lint, npm run typecheck, npx --yes bun@1.3.9 test --timeout 20000 (142 passed, 3 gated skips), V1 TypeScript build, and V2 bundle build.