Remove compact_assistant_xml, compact_assistant_xml_selective, _xml_replacer,
_build_tc_lookup and _TOOL_USE_RE. These functions compact inline
<tool_use name=... id=...>...</tool_use> XML blocks inside assistant message
content, which only exist on providers that don't natively support
tool_use blocks (e.g. AWS Bedrock socle in bouzecode). Upstream cheetahclaws
uses the native Anthropic content: [{"type":"tool_use", ...}] format, so
these functions early-returned on every call and the compact_tool_history
branch that invoked compact_assistant_xml was a no-op.

Also fix _apply_context_gc which was wrapped in a double try/except where
the outer pass was unreachable, and which imported only apply_gc while
referencing inject_notes and prepend_verbatim_audit (NameError when
gc_state had entries). Replaced with a single try that imports all three
names and cleanly returns on ImportError if PR SafeRL-Lab#55 isn't deployed
alongside.

Test file drops the TestCompactAssistantXml / TestCompactAssistantXmlSelective
classes that exercised the removed functions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…, thinking strip, cache breakpoint