fix(agent-core): tier anti-repeat reminders at streak counts 3, 5, and 8

[sailist]

Summary

Replace the single threshold of 7 with tiered reminders triggered at streak counts 3, 5, and 8. The first reminder is a generic nudge, while the second and third include the tool name, repeat count, and arguments for stronger guidance.

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1. Tiered anti-repeat reminders

Problem: The previous anti-repeat mechanism used a single threshold (7 consecutive identical tool calls) to remind the agent, which provided too little feedback early and too much all at once.

What was done:

• Introduced three reminder tiers at streak counts 3, 5, and 8.
• The first tier (count 3) sends a generic nudge.
• The second tier (count 5) and third tier (count 8) include the tool name, repeat count, and arguments to give the agent stronger, more actionable guidance.
• Updated the corresponding test suite to cover all three tiers and verify message content.
• Added a changeset documenting the fix.

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Checklist

• I have read the CONTRIBUTING document.
• I have linked the related issue, if any.
• I have added tests that prove my fix is effective or that my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.