fix(opencode): inject recalled context via system.transform hook

[pszymkowiak]

Summary

Closes #169.

The previous `session.created` handler only logged a debug line — it never actually delivered recalled memories into the session. OpenCode's `session.created` is observational; the API for context injection is `experimental.chat.system.transform`, which fires before each model call and lets a plugin push extra system-prompt strings.

Fix

New Layer 3 handler in the plugin that:

• Runs once per session (de-dup by sessionID so the wake-up doesn't re-inject on every chat turn).
• Captures `icm wake-up --project

  ` (critical/high facts + preferences) → pushes to `output.system`.

• Captures `icm recall-project --limit 5` (top project memories) → pushes to `output.system`.

Both calls are best-effort — a missing binary or empty memory store returns "" and silently no-ops.

Why `experimental.chat.system.transform`

Verified against `@opencode-ai/plugin@1.14.46`:

```ts
"experimental.chat.system.transform"?: (input: { sessionID?, model }, output: { system: string[] }) => Promise
```

This is the only hook that lets a plugin add to the system prompt. `chat.params` only modifies model parameters (temperature etc.), `chat.message` mutates the user message itself.

Test plan

• Smoke-tested both CLI commands the plugin shells out to (`icm wake-up --project icm`, `icm recall-project --limit 3`) — both produce non-empty stdout
• `tsc --strict` against `@opencode-ai/plugin@1.14.46` — clean
• `cargo test --workspace` — 423 passed (no Rust changes; verified suite still green)
• `cargo clippy --all-targets -- -D warnings` — clean
• Other layers preserved: tool.execute.after extraction, experimental.session.compacting extraction, session.created log

🤖 Generated with Claude Code