fix(web_tools): trigger plugin discovery before registry dispatch (#27683)

[luyao618]

Summary

Closes #27683.

tools/web_tools.py dispatches to providers from agent.web_search_registry at three sites — web_search_tool (~L797), web_extract_tool (~L935), and web_crawl_tool (~L1193) — without first calling hermes_cli.plugins._ensure_plugins_discovered().

On a fresh install (or any session where plugin discovery hasn't already been triggered for some unrelated reason), the registry is empty. get_provider() and get_active_*_provider() therefore return None, and the user gets a "No web search/extract/crawl provider configured" error envelope — or a silent fallback — even though they have a backend (e.g. ddgs) installed and configured.

The sibling tools tools/image_generation_tool.py and tools/video_generation_tool.py both already guard against this exact failure mode by lazily importing and calling _ensure_plugins_discovered() before consulting their respective registries (see image_generation_tool.py:874, video_generation_tool.py:207). web_tools.py was the outlier.

Fix

Mirror the existing pattern at all three dispatch sites — a 6-line try/except block immediately before the agent.web_search_registry import:

try:
    from hermes_cli.plugins import _ensure_plugins_discovered

    _ensure_plugins_discovered()
except Exception:
    pass

• Lazy import inside the function body so we don't perturb module-level import order.
• except Exception so the path still works in slim/test environments where hermes_cli isn't importable (matches the defensive style in image_generation_tool.py).
• Idempotent + cheap on subsequent calls — _ensure_plugins_discovered() short-circuits after the first run.
• No provider-resolution semantics are changed.

Tests

New file tests/tools/test_web_tools_plugin_discovery.py adds three regression tests, one per dispatcher. Each patches hermes_cli.plugins._ensure_plugins_discovered, forces the registry to return None (so the tool short-circuits quickly), and asserts the discovery hook was invoked.

I verified both directions:

$ pytest tests/tools/test_web_tools_plugin_discovery.py -x -q     # on main (before fix)
3 failed in 6.01s

$ pytest tests/tools/test_web_tools_plugin_discovery.py -x -q     # with this patch
3 passed in 8.70s

Scope

• tools/web_tools.py — 18 lines added (three 6-line blocks), no other edits, no formatting churn.
• tests/tools/test_web_tools_plugin_discovery.py — new file, 111 lines.

Risk

Very low. Discovery is already invoked by image/video tools on every call; this brings web tools in line. The try/except Exception keeps the slim-environment path safe.

[alt-glitch]

Duplicate of #27584 which already fixes the same missing _ensure_plugins_discovered() calls in web_tools.py (for #27580). The referenced issue #27683 was itself flagged as a duplicate of #27580.

[bbernstein616]

Watchdog review: independently checked the patch and ran targeted verification locally. The change matches the existing image/video lazy plugin-discovery pattern, keeps import-order risk low, and all CI checks are green. Local verification: scripts/run_tests.sh tests/tools/test_web_tools_plugin_discovery.py (3 passed) and python -m ruff check tests/tools/test_web_tools_plugin_discovery.py tools/web_tools.py (passed). I attempted to merge, but this token/user lacks MergePullRequest permission.

[luyao618]

Closing as duplicate of #27584 (same _ensure_plugins_discovered() fix in web_tools.py, also open). Deferring to that PR.