feat(opencode): capture console output and surface it to the model

- console.log/warn/error/info/debug are now a real Rune interpreter builtin:
  a seeded global that formats its args (strings verbatim, objects/arrays as
  JSON, space-joined) and appends a line to a per-run LogCollector. It is not a
  tool call (spends no tool-call budget), returns undefined, and any other
  member throws. Formatting is charged to maxOperations and total captured
  output is bounded by maxAuditBytes so a logging loop can't exhaust memory.
- The collector is shared by reference with parallel interpreter forks (like the
  operation budget) and lives in execute()'s outer scope, so logs are surfaced
  on every ExecuteResult path — success, thrown error, and timeout.
- ExecuteResult (and its schema) gain a logs field; code mode appends captured
  logs to the model-facing output as a trailing '[level] message' section on
  both the success and error paths (withLogs). Logs go to the model only.
- Documents console in rune.md; drops the now-satisfied 'not done yet' entry.

packages/opencode/test/session/code-mode.test.ts

@@ -9,6 +9,7 @@ import {
   rankTools,
   renderType,
   toEnvelope,
+  withLogs,
   type SearchEntry,
 } from "@/session/code-mode"
 import type { Tool as MCPToolDef } from "@modelcontextprotocol/sdk/types.js"
@@ -406,6 +407,17 @@ describe("code mode execute", () => {
     expect(formatValue(undefined)).toBe("undefined")
   })
 
+  test("unit: withLogs", () => {
+    // No logs: output is returned untouched.
+    expect(withLogs("result", [])).toBe("result")
+    // Logs are appended as a trailing section, one `[level] message` line each.
+    expect(withLogs("result", [{ level: "log", message: "a" }, { level: "warn", message: "b" }])).toBe(
+      "result\n\nLogs:\n[log] a\n[warn] b",
+    )
+    // Empty output still gets the section (no leading blank lines).
+    expect(withLogs("", [{ level: "error", message: "boom" }])).toBe("Logs:\n[error] boom")
+  })
+
   test("terminates a runaway loop via the operation limit instead of hanging", async () => {
     const tool = await build({})
     const output = await Effect.runPromise(tool.execute({ code: "while (true) {}" }, ctx))