feat(dist): ship via GitHub Release binaries + install.sh (drop npm as primary)

Distribute the prebuilt binary through GitHub Releases instead of the npm
registry — zero auth for the publisher (CI's GITHUB_TOKEN) and zero auth for
consumers (no npm token / 2FA / OTP, no GitHub Packages .npmrc).

- install.sh: detects OS/arch (incl. linux musl), downloads the matching
  agent-browser-<platform>.tar.gz from the GitHub Release, verifies .sha256,
  installs `agent-browser` + `abs` to /usr/local/bin or ~/.local/bin.
  Override via AGENT_BROWSER_VERSION / AGENT_BROWSER_BIN_DIR.
- .github/workflows/release-binaries.yml: on tag push (v*), build all 7
  platform variants (reusing the zigbuild cross-compile matrix), package each
  as .tar.gz + .sha256, attach to the tag's GitHub Release. No npm, no token.
- remove .github/workflows/release.yml: it published to npm (--provenance) and
  built the (removed) dashboard, so it broke on every main push.
- README install now leads with `curl … install.sh | sh`; npm demoted to a
  legacy alternative.
- skill stub self-heals: if `agent-browser` is missing, run install.sh (don't
  fall back to other browser tools).

skills/agent-browser/SKILL.md

@@ -10,7 +10,13 @@ hidden: true
 Fast browser automation CLI for AI agents. Chrome/Chromium via CDP with
 accessibility-tree snapshots and compact `@eN` element refs.
 
-Install: `npm i -g agent-browser && agent-browser install`
+**Install / self-heal:** if the `agent-browser` (or `abs`) command is missing —
+e.g. a command errors with "command not found" — install it from the GitHub
+Release (no npm, no token), then retry. Do NOT fall back to other browser tools:
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/leeguooooo/agent-browser-stealth/main/install.sh | sh
+```
 
 ## Start here