test(compress): re-initialise main_runtime attrs in manually-built compressor

[luigileap]

Problem

tests/agent/test_compress_focus.py::test_focus_topic_injected_into_summary_prompt
and test_no_focus_topic_no_injection fail with:

WARNING  root:context_compressor.py:477 Failed to generate context summary:
'ContextCompressor' object has no attribute 'model'.  Further summary
attempts paused for 600 seconds.

Both tests then report result is None / KeyError: 'messages' because
_generate_summary swallowed the AttributeError in its broad-except
cooldown path.

Root cause

_make_compressor in the test file builds a compressor with
ContextCompressor.__new__(ContextCompressor), bypassing __init__, and
explicitly sets only the attributes the method used to touch (token
budgets, protect counts, the previous-summary cache, etc.).

PR #7910 ("fix(agent): route compression aux through live session
runtime") added a main_runtime dict to the call_llm invocation inside
_generate_summary:

"main_runtime": {
    "model": self.model,
    "provider": self.provider,
    "base_url": self.base_url,
    "api_key": self.api_key,
    "api_mode": self.api_mode,
},

Production sets those attributes in __init__, but the test fixture —
which predates the runtime-aware change — never did. Accessing
self.model raises AttributeError, which the method catches and
converts into a 10-minute cooldown + None return.

Fix

Extend _make_compressor to set the five runtime attributes
(model, provider, base_url, api_key, api_mode) so the fixture
matches the current production surface.

Verification

$ python -m pytest --override-ini="addopts=" -q tests/agent/test_compress_focus.py
....                                                                     [100%]
4 passed in 0.53s

All four tests in the module pass, including the previously failing two.

[kshitijk4poor]

Already fixed on main via #9483 (commit 2558d28). The compressor fixture attributes are now set. Thanks!