feat: add task context classification to coordinator acknowledgment

[diberry]

Summary

Adds a task context classification requirement to the coordinator's "Acknowledge Immediately" prompt. Before naming agents, the coordinator now signals how the user's message relates to the conversation:

• 🔗 Continuing — extends the same task thread
• 🆕 New task — unrelated to previous work
• 🔀 Related pivot — connected but shifts focus

Closes #359

Motivation

In multi-turn sessions, users often can't tell whether the system recognizes their message as part of ongoing work or a fresh request. The generic agent launch table doesn't provide this context. Adding a one-line classification signal as the first line of every acknowledgment solves this without any code changes.

What Changed

File: .github/agents/squad.agent.md
Section: "Acknowledge Immediately — Feels Heard"
Change: Added "Task Context Signal" sub-section with three classification signals and updated examples.

UX Before / After

Before

🔧 EECOM — fixing the auth handler
🧪 Sims — writing test cases

After (continuing previous auth work)

🔗 Continuing your auth refactor

🔧 EECOM — fixing the auth handler
🧪 Sims — writing test cases

After (new unrelated task)

🆕 New task

📝 PAO — drafting the README

After (pivoting from auth to tests)

🔀 Related pivot from the auth work — now looking at tests

🧪 Sims — writing regression tests
📋 Scribe — logging session

Documentation Impact

• The change IS documentation (prompt governance)
• No external docs affected
• Agent behavior changes immediately in new sessions; existing sessions use the old prompt until restarted

Testing

• No code changes — no build, no tests needed
• Verification: Start a new Squad session, send 2+ messages, observe that the coordinator classifies each response with the appropriate signal
• First message of a session should NOT have a signal (no prior context)

Rollback Plan

Revert the single commit — removes the sub-section, restores original examples.

Review Checklist

• Signal wording is clear and not jargon-heavy
• Examples use current team names from the active casting universe
• The "skip on first message" rule is clear
• No breaking changes to existing coordinator behavior

[diberry]

@bradygaster This would give me feedback so I know the Squad is doing what I am directing it to do instead of a linear progression of feedback disconnected from each other.