release: prepare v1.3.0

[paralta]

Prepares the v1.3.0 release of the JavaScript SDK, mirroring the equivalent changes in dir-sdk-python v1.3.0.

Changes

• Bumped SDK to v1.3.0 and pinned @buf/agntcy_dir.bufbuild_es to the buf SDK generated from agntcy/dir v1.3.0, including matching updates to CHANGELOG.md, RELEASE.md, the issue template, and lockfiles — required to track the new server release.
• Bumped the directory Helm chart and dirctl image used in CI to v1.3.0 — so integration tests run against the matching server version.
• Added an npm version badge to README.md — gives users a clear, at-a-glance view of the latest published version.
• Consolidated Taskfile.deps.yml, Taskfile.test-env.yml, and Taskfile.vars.yml into a single Taskfile.yml — reduces fragmentation.
• Removed .github/dependabot.yml and .github/pull_request_template.md — Renovate is the only dependency manager used here, and PR templates are not adopted in other repos.
• Removed .github/workflows/lint.yml and .github/linters/ (markdownlint + yamllint configs) — the super-linter workflow was permanently disabled and not used.
• Removed .github/workflows/dependency.yml — the dependency-review action was disabled and unused; CodeQL already covers vulnerability scanning.
• Removed .cz.toml — Commitizen is not part of the release process.
• Removed .prettierrc — Prettier was never installed nor invoked by any script; the file had no effect.
• Removed eslint.config.mjs, the lint/fix npm scripts, and typescript-eslint from devDependencies — the config imported @eslint/js which was never installed (lint was silently broken) and was not run in CI or Taskfile.
• Trimmed .gitignore down to only JS-relevant entries — dropped Python, Helm, Go, MCP, and Flutter GUI sections inherited from the parent dir mono-repo that don't apply here.