chore: prepare v1.14.4-pre release

[EhabY]

Summary

• bump the extension version from 1.14.3 to 1.14.4 for the next pre-release tag v1.14.4-pre
• update CHANGELOG.md with the full user-facing changes since v1.14.3
• keep the changelog focused on discoverable behavior changes and include CLI docs links for the new diagnostics commands

Testing

• pnpm format:check

Disclosure: This PR description was generated by Coder Agents.

Plan

1. Create branch chore/release-v1.14.4-pre
2. Bump package.json from 1.14.3 to 1.14.4
3. Replace ## Unreleased in CHANGELOG.md with ## [v1.14.4-pre](https://github.com/coder/vscode-coder/releases/tag/v1.14.4-pre) 2026-04-20
4. Consolidate the user-facing changes since v1.14.3
5. Commit, push, and open a PR

Reviewer notes:

• update-related fixes are split into separate bullets for the update flow and outdated notifications
• diagnostics commands are listed separately with additional detail and links to the CLI docs
• internal-only work like CI, dependency bumps, and refactors is intentionally omitted from the changelog