Terminal window and Git source control are still not supported in Web Console

**Is your feature request related to a problem? Please describe.**

The Web Console still has no working terminal, and no Git source control support either.

- **Terminal** — the panel was hidden in #11 / forcedotcom/code-builder-web#84 rather than enabled, so there is currently no way to run shell or CLI commands from inside the Web Console. Anything CLI-driven — `sf` commands, npm scripts, log tailing, custom scripts — requires leaving the Web Console for Code Builder or a local environment.
- **Git source control** — there is no source control view and no `git` available, so cloning a repo, staging and committing changes, branching, resolving conflicts, and pushing/pulling are all impossible from the Web Console. Work has to be moved elsewhere just to get it into version control.

Together these two gaps mean the Web Console cannot support a normal end-to-end development loop on its own.

**Describe the solution you'd like**

A supported, functional integrated terminal:

- A shell session scoped to the current sfdx project workspace
- `sf` CLI pre-authenticated against the connected org
- Multiple terminal tabs, persisting across page reloads

Plus first-class Git source control:

- A source control panel (changes, staging, commit, diff view) comparable to the VS Code SCM view
- Clone / branch / merge / pull / push against GitHub and other remotes
- Credential handling for private repos
- `git` available on the terminal path as well, for anything the UI does not cover

**Describe alternatives you've considered**

- Switching to Code Builder for CLI and Git work — breaks flow and duplicates setup
- Running commands locally against the same org — defeats the purpose of a browser-based console

**Additional context**

Related: #11 (terminal hidden because it "can't be used"), forcedotcom/code-builder-web#84.

No implementation files or tests are identified. Start by reviewing related issue #11 and forcedotcom/code-builder-web#84, then determine where terminal and source-control support belong. Done means the Web Console has a functional workspace terminal and Git workflow covering the requested capabilities.

Written by the indexing model from the issue text.