feat: initial commit — extracted from comfy-cloud

Anything-can-drive-the-UI command bus. Single dispatch point for LLM tool
calls, scripts, and (optional) WebSocket remote control. JSON canonical
form plus a plain-text DSL sugar layer. Includes a visible virtual cursor
that animates to elements before commands act on them.

Modules:
- bus.ts        — CommandBus class, dispatch, handlers, vars, history,
                  listActions, readState. Built-in handlers: navigate, click,
                  fill, submit, select, wait, wait_for, scroll, read, expect,
                  set
- parser.ts     — DSL ↔ JSON, with quoted values, # comments, # speed:
                  directive, $name = <cmd> assignment, $var interpolation,
                  expect assertions
- script.ts     — script runner; loads /scripts/<name>.script, supports
                  sub-scripts via `run` command
- cursor.ts     — virtual cursor + ripple, speed-controlled, aria-hidden
- provider.tsx  — React glue: registers `navigate` via react-router, mounts
                  cursor, exposes window.commandBus / runScript /
                  runScriptText for console use
- ws.ts         — optional WebSocket producer (connectCommandSocket)
- llm-bridge.ts — buildSystemPrompt (DSL ref + live action snapshot),
                  extractActionBlocks, runActionBlocks, estimateTokens,
                  trimMessages
- index.tsx     — barrel re-exports

Peer deps: react, react-router (consuming app provides).

Originally inline in `comfy-cloud/app/lib/`. Extracted as part of the
crema-app-aifirst-template scaffolding.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/llm-bridge.ts

@@ -0,0 +1,102 @@
+// LLM ↔ command bus glue.
+// - buildSystemPrompt() teaches the model the DSL and lists the actions
+//   currently visible on screen.
+// - extractActionBlocks() pulls ```action ... ``` blocks from assistant text.
+// - runActionBlocks() executes them through the script runner.
+
+import { commandBus } from "./bus"
+import { runScriptText } from "./script"
+
+const DSL_REFERENCE = `To act on the UI, emit a fenced \`\`\`action ... \`\`\` block. One command per line.
+
+Commands: navigate <path> | click <target> | fill <target> "<value>" | submit <target> | select <target> <value> | wait <ms> | wait_for <target> | scroll [<target>] | read [<target>] | expect <target> to_contain "<text>" | expect <target> to_be_visible | expect <target> to_have_value "<text>"
+
+Rules: only emit a block when asked to do something. Use only target ids from "Available actions". Short sentence + block. Quote values with spaces. Comments start with #.
+
+Example — User: "go to resources" → "On it.\n\n\`\`\`action\nnavigate /resources\n\`\`\`"`
+
+export type SystemPromptContext = {
+  /** Optional preface specific to the app/persona. */
+  preface?: string
+  /** Current route pathname. */
+  path?: string
+  /** Whether to inject the live action snapshot. */
+  includeActions?: boolean
+}
+
+export function buildSystemPrompt(ctx: SystemPromptContext = {}): string {
+  const parts: string[] = []
+  parts.push(
+    ctx.preface ??
+      "You are the assistant in Comfy Cloud. Answer concisely and drive the UI when asked.",
+  )
+  parts.push(DSL_REFERENCE)
+
+  if (ctx.includeActions !== false) {
+    const actions = commandBus.listActions().filter((a) => a.visible)
+    const path = ctx.path ?? (typeof window !== "undefined" ? window.location.pathname : "")
+    parts.push(`Route: ${path || "?"}\nAvailable actions:\n${
+      actions.length === 0
+        ? "(none)"
+        : actions.map((a) => `- ${a.id}${a.label ? `: ${a.label}` : ""}`).join("\n")
+    }`)
+  }
+
+  return parts.join("\n\n")
+}
+
+/** Rough token estimate: ~4 chars per token. Good enough for budgeting. */
+export function estimateTokens(text: string): number {
+  return Math.ceil(text.length / 4)
+}
+
+/** Trim a message list to fit a token budget, preserving the most recent turns. */
+export function trimMessages<T extends { content: string }>(
+  messages: T[],
+  budgetTokens: number,
+): T[] {
+  let used = 0
+  const kept: T[] = []
+  for (let i = messages.length - 1; i >= 0; i--) {
+    const t = estimateTokens(messages[i].content)
+    if (used + t > budgetTokens) break
+    kept.unshift(messages[i])
+    used += t
+  }
+  return kept
+}
+
+const ACTION_BLOCK_RE = /```action\s*\n([\s\S]*?)```/g
+
+export function extractActionBlocks(text: string): string[] {
+  const blocks: string[] = []
+  let m: RegExpExecArray | null
+  ACTION_BLOCK_RE.lastIndex = 0
+  while ((m = ACTION_BLOCK_RE.exec(text)) !== null) {
+    blocks.push(m[1].trim())
+  }
+  return blocks
+}
+
+export type RunActionBlocksResult = {
+  ran: number
+  errors: string[]
+}
+
+export async function runActionBlocks(
+  text: string,
+  opts: { signal?: AbortSignal } = {},
+): Promise<RunActionBlocksResult> {
+  const blocks = extractActionBlocks(text)
+  const errors: string[] = []
+  let ran = 0
+  for (const block of blocks) {
+    try {
+      await runScriptText(block, { signal: opts.signal })
+      ran++
+    } catch (e) {
+      errors.push(e instanceof Error ? e.message : String(e))
+    }
+  }
+  return { ran, errors }
+}