Add CLI support for naming and renaming tabs

[adamgall]

What problem does this solve?

Supacode already lets users assign a persistent custom title to a terminal tab through Rename Tab (via right-click context menu), but the CLI cannot name a tab when creating it or rename an existing tab.

Scripts can create and target tabs by UUID, yet cannot give those tabs stable role-based names. For example, a repository setup script may create a repeatable layout with scratch, implement, git, and review tabs. It can capture every ID returned by supacode tab new, but the resulting tabs still have to be renamed manually.

A terminal/OSC title is not an equivalent workaround: it is process-controlled, may change while a command is running, and is distinct from Supacode's persisted customTitle override.

Proposed solution

Give tab creation and tab renaming equal support in the CLI.

Name a tab atomically when creating it:

implement_tab="$(supacode tab new \
  -w "$SUPACODE_WORKTREE_ID" \
  --title "implement" \
  -i "omp")"

Rename an existing tab:

supacode tab rename \
  -w "$SUPACODE_WORKTREE_ID" \
  -t "$tab_id" \
  --title "review"

Both operations should use the same persistent custom-title behavior as the existing UI action. Specifically:

• supacode tab new --title <title> should set the new tab's customTitle as part of creation.
• supacode tab rename --title <title> should update an existing tab's customTitle.
• -w and -t should default from SUPACODE_WORKTREE_ID and SUPACODE_TAB_ID wherever applicable, consistent with the other tab commands.
• The custom title should survive terminal title changes and app restarts.
• Renaming with an empty title should clear the custom-title override, matching the existing model behavior.
• Both operations should return the normal CLI acknowledgement or a useful error when the worktree or tab does not exist.
• Both operations should participate in the existing automated-action confirmation policy.

Alternatives considered

• Rename tabs manually through the context menu: works, but cannot be used by repository setup scripts that create a standard layout.

Supacode version

0.10.6

Are you planning to build this yourself?

• I intend to open a pull request once this is approved and marked ready.

Before submitting

• I searched existing issues and this is not a duplicate.
• I understand feature pull requests are closed until the issue is marked ready.
• I agree to follow this project's Code of Conduct.

[github-actions]

Thanks for your patience. This feature is approved and marked ready, so it is now open for a pull request. If you'd like to work on it, open a pull request and link it with Closes #659 in the description. If the issue is assigned to someone, it is reserved for them; otherwise anyone is welcome to pick it up.

See CONTRIBUTING.md for the full flow.

[adamgall]

Working on this one now