`_module_registers_tools()` reads each `tools/*.py` file and fully
AST-parses it to check for a top-level `registry.register()` call.
90 files are scanned on every process start — but only 32 actually
register tools.
Add a cheap text prefilter: after reading the file (which we need to
do anyway for AST), check that both `"registry"` and `"register"`
appear in the source before calling `ast.parse`. A file with a
top-level `registry.register()` call must contain both strings, so
this is a perfect superset — zero false negatives. 50 of 90 files
skip the AST parse entirely.
The `source=` parameter is not threaded through `discover_builtin_tools`;
the prefilter lives entirely inside `_module_registers_tools`, keeping
the public API unchanged.
Benchmark (median of 10 runs, scanning 90 files):
before (read + ast.parse all): 305.9ms
after (text prefilter + ast): 187.8ms
speedup: 1.6x (118ms saved)
Identical module set: 32 modules, same names, same order.
ethernet
2d71e2f1e4