feat(cli): esrun upgrade (self-update); doc fixes; surface CLI types on site

- esrun upgrade: built-in self-update — finds the latest GitHub release for the
  target, downloads/extracts it, and replaces the running binary in place
  (self_update + rustls). Mirrors the installer. USAGE + install page updated to
  use it instead of re-running curl.
- site: document `esrun upgrade` and `esrun types` on the /api/cli page
  (options + usage), incl. the @opentf/esrun-types package
- guide: multi-line the loop examples (no more cramped single-line for/await)
- fs page: Glob example is a clean one-liner (match), not a single-line loop

Author: Thanga-Ganapathy

CHANGELOG.md

@@ -8,6 +8,11 @@ pre-`0.1.0` and the public API is unstable.
 
 ### Added
 
+- **`esrun upgrade`** — self-update built into the CLI: finds the latest GitHub
+  release for the platform, downloads + extracts it, and replaces the running
+  binary in place (rustls TLS, via `self_update`). The Installation page's
+  Upgrade step now uses it.
+
 - **`@opentf/esrun-types`** — hand-written TypeScript definitions for the
   `runtime:` standard modules (`runtime:process`, `runtime:path`, `runtime:fs`),
   in [`types/`](types/), for editor completion and type-checking. Ambient