fix(compressor): reset _summary_failure_cooldown_until in on_session_reset()

[nftpoetrist]

What does this PR do?

ContextCompressor.on_session_reset() clears _previous_summary, _last_summary_error, and _ineffective_compression_count but leaves _summary_failure_cooldown_until intact. When a transient summary error (network timeout, rate limit) sets a 60 s cooldown — or 600 s when no auxiliary provider is configured — and the user immediately runs /reset or /new, the cooldown carries into the new session. If the new session reaches the compression threshold before the cooldown expires, _generate_summary() returns None early: middle turns are silently dropped without a summary and the agent continues with no indication that compaction was skipped.

One-line fix in on_session_reset(): set _summary_failure_cooldown_until = 0.0, matching the value assigned in __init__ and symmetric with the other per-session fields already cleared there. Scoped to session reset only — no behavior change for sessions that never hit an error.

Related Issue

Fixes #15547

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests
• ♻️ Refactor
• 🎯 New skill

Changes Made

• agent/context_compressor.py: add self._summary_failure_cooldown_until = 0.0 to on_session_reset() (+1 line)

How to Test

1. Trigger a context compression failure (disable auxiliary provider or simulate a network error in _generate_summary)
2. Confirm _summary_failure_cooldown_until is set to a future timestamp
3. Call on_session_reset()
4. Assert _summary_failure_cooldown_until == 0.0

import time
from unittest.mock import patch

with patch("agent.context_compressor.get_model_context_length", return_value=100000):
    c = ContextCompressor(model="test/model", quiet_mode=True)

c._summary_failure_cooldown_until = time.monotonic() + 60
c.on_session_reset()
assert c._summary_failure_cooldown_until == 0.0

Checklist

Code

• Contributing Guide okundu
• Conventional Commits
• Duplicate PR yok
• Sadece bu fix
• pytest çalıştırıldı
• Platform: macOS

Documentation & Housekeeping

• Docs güncellendi — N/A
• cli-config.yaml.example — N/A
• CONTRIBUTING.md/AGENTS.md — N/A
• Cross-platform impact — N/A
• Tool descriptions — N/A

[teknium1]

Salvaged via #19622 onto current main - your commit authorship was preserved. Thanks!