Add the harness, envs, per-bot models and chat attachments

- Harness: providers, model catalog synced hourly, automatic free picks,
  cooldowns, tool loop with context trimming, MCP computer tools
- Bots queue runs replies and tasks through the harness; jobs wait
  (attempt refunded) while every model is resting
- Envs: Settings > Environment, scoped general/workspace/computer,
  written to computers and redacted from tool output
- Models: Settings > Models, per-harness provider select defaulting to
  OpenRouter, and a models modal on each bot's chat (the coordinator's
  edits the defaults)
- Chat: thinking row while a reply runs, file attachments (upload,
  paste, drop) that replies read as images, audio and document text
- Fix media uploads failing after a user's first file, and private
  files being served from the public media path

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/harness/tools/computer/compose-computer-env-files.ts

@@ -0,0 +1,18 @@
+type Params = {
+    envs: { key: string; value: string }[];
+};
+
+/**
+ * A computer's env files: `shell` for bash (`export KEY='value'`, single
+ * quotes escaped) and `json` for code runners.
+ */
+export default function composeComputerEnvFiles({ envs }: Params) {
+    const shell = envs
+        .map((env) => `export ${env.key}='${env.value.replaceAll("'", `'\\''`)}'`)
+        .join("\n");
+
+    return {
+        shell: shell ? `${shell}\n` : "",
+        json: JSON.stringify(Object.fromEntries(envs.map((env) => [env.key, env.value]))),
+    };
+}