core: consolidate shared infrastructure into core package

Moves effect logging, observability, runtime utilities, flags, installation
version info, and process utilities from opencode to core package. This
enables better code sharing across packages and establishes core as the
single source of truth for foundational utilities.

All internal imports updated to use @opencode-ai/core paths for consistency.

packages/core/src/util/opencode-process.ts

@@ -0,0 +1,24 @@
+export const OPENCODE_RUN_ID = "OPENCODE_RUN_ID"
+export const OPENCODE_PROCESS_ROLE = "OPENCODE_PROCESS_ROLE"
+
+export function ensureRunID() {
+  return (process.env[OPENCODE_RUN_ID] ??= crypto.randomUUID())
+}
+
+export function ensureProcessRole(fallback: "main" | "worker") {
+  return (process.env[OPENCODE_PROCESS_ROLE] ??= fallback)
+}
+
+export function ensureProcessMetadata(fallback: "main" | "worker") {
+  return {
+    runID: ensureRunID(),
+    processRole: ensureProcessRole(fallback),
+  }
+}
+
+export function sanitizedProcessEnv(overrides?: Record<string, string>) {
+  const env = Object.fromEntries(
+    Object.entries(process.env).filter((entry): entry is [string, string] => entry[1] !== undefined),
+  )
+  return overrides ? Object.assign(env, overrides) : env
+}