fix(file-ops): allow file search in hidden roots

[fmercurio]

Summary

• allow search_files(target="files") to return results when the explicit search root is inside a hidden directory, e.g. ~/.hermes/logs
• keep the find fallback excluding hidden descendant files/directories for normal roots
• add regression tests for hidden-root searches and normal hidden-descendant filtering

Root cause

When rg is unavailable, the file search fallback uses find ... -not -path '*/.*' to mimic ripgrep's hidden-directory behavior. If the caller explicitly searches a hidden root like /Users/me/.hermes/logs, every result path contains /.hermes/, so the filter removes all files and returns total_count=0.

Test plan

• scripts/run_tests.sh tests/tools/test_file_operations.py -q -k 'SearchFilesFallbackHiddenPaths or SearchPathValidation'
• scripts/run_tests.sh tests/tools/test_file_operations.py -q

[fmercurio]

I can confirm this still reproduces on current origin/main after updating.

In a live Hermes gateway session, search_files(target="files", path="/Users/.../.hermes/...") returned total_count=0 even though matching files existed. The agent then interpreted it as “no content”.

The root cause appears unchanged on current origin/main in tools/file_operations.py:

hidden_exclude = "-not -path '*/.*'"

Because the explicit search root itself contains a hidden path component (.hermes), every result path matches */.* and gets filtered out.

I reapplied this PR's fix locally and verified the repro succeeds: it returns the expected file under the explicit hidden root while still excluding hidden descendants like .hub/.

Local verification:

58 passed, 2 skipped

So this is still affecting current users after update; it would be great to get this merged or consolidated with the newer related PRs (#18487 / #18645).

[teknium1]

Salvaged via #19878 onto current main - your commit authorship was preserved. Thanks!