Dashboard: show task title under task ID in lane view

[HenryLach]

Problem

The lane view in the dashboard shows only the task ID (e.g., TP-165) with no indication of what the task actually does. The operator has to click into the task or remember task IDs to understand what each lane is working on.

Current display:

●  👁 TP-165                    ● running    11m 11s    ━━━━━━━━━  0% 0/18

Proposed Solution

Add a subtitle line under the task ID showing the task title, extracted from the # Task: header in PROMPT.md:

●  👁 TP-165                    ● running    11m 11s    ━━━━━━━━━  0% 0/18
      Segment Boundary .DONE Guard and Expansion Consumption

The subtitle should be:

• Smaller font size / muted color (secondary text treatment)
• Truncated with ellipsis if the title is very long
• Extracted from the first line of PROMPT.md: # Task: TP-165 - {title}

Implementation Notes

• The title can be parsed from PROMPT.md at batch start (or lazily on first dashboard load) with a simple regex: /^# Task: \S+ - (.+)$/m
• The server (dashboard/server.cjs) already reads task folders for STATUS.md — adding a PROMPT.md title read is straightforward
• The title is static (PROMPT.md is immutable) so it can be cached once per batch
• Could also be included in the batch state task records to avoid repeated file reads

Screenshot

Current lane view (no title):

(Task ID only — operator must remember what TP-165 means)