fix(tui): restore agent name in task progress display

[zerone0x]

Issue for this PR

Closes #15915

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The v1.2.16 TUI refactor (PR #15607) replaced BlockTool with InlineTool for task rendering. The old BlockTool title was "# AgentName Task" — it showed the subagent_type (e.g. "Explore", "General"). The new inline renderer only builds Task ${description}, so the agent name is gone.

Fix: compute an agentPrefix from props.input.subagent_type (titlecased) and prepend it. The output becomes:

│ Explore: Task Verify Refit cancellation behavior
└ 22 toolcalls · 1m 1s

Falls back to plain Task description when subagent_type is absent. Locale.titlecase is already used on the same line for the tool name in the running-state line, so the pattern is identical to existing code.

How did you verify your code works?

Code diff reviewed against the old BlockTool title format and the new InlineTool content memo. The Locale.titlecase helper is already called in the same content memo (line 1982 for current().tool), so no new imports are needed.

Screenshots / recordings

UI change; no terminal recording attached but the format is text-only.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[zerone0x]

The e2e failure is unrelated to this change. The failing test is:
[chromium] › e2e/projects/projects-switch.spec.ts:49 › switching back to a project opens the latest workspace session

It throws SQLiteError: FOREIGN KEY constraint failed in session/index.ts:691 — session database management, nothing to do with TUI task tool rendering. The same test suite passes on the concurrent PR #15948 and on fix/tui-thread-exit-cleanup, confirming this is a flaky test (or a regression introduced by the workspace rework in #15895 that merged right before this PR was submitted).