fix(agent): bash/python/web_search absent from tool schemas on low-signal turns when workspace is set and tools are enabled

[jdmanring]

Bug

When a workspace is active and Shell Access and/or Web Search are enabled, the agent reports no access to `bash`, `python`, or `web_search` for vague or short opening messages.

Root Cause

`agent_loop.py` has a fast path for low-signal turns when a workspace is active. It builds `_relevant_tools` from scratch:

```python
_relevant_tools = set(ALWAYS_AVAILABLE)
_relevant_tools |= (_DOMAIN_TOOL_MAP["files"] & PLAN_MODE_READONLY_TOOLS)
```

`PLAN_MODE_READONLY_TOOLS` includes `web_search` and `web_fetch` but not `bash` or `python`. `_DOMAIN_TOOL_MAP["files"]` includes `bash` and `python` but not `web_search` or `web_fetch`. The intersection excludes all three.

The fast path never consults `disabled_tools`. The Shell Access and Web Search toggles only prevent tools from entering `disabled_tools` — they do not add tools to `_relevant_tools`. Since the fast path builds `_relevant_tools` from scratch and then skips RAG retrieval (the set is already non-empty), the domain-based additions that would normally include `web_search` never run.

Fix

Consult `disabled_tools` in the workspace fast path to include tools the user explicitly enabled:

```python
if "bash" not in disabled_tools:
_relevant_tools.add("bash")
if "python" not in disabled_tools:
_relevant_tools.add("python")
if "web_search" not in disabled_tools:
_relevant_tools.add("web_search")
_relevant_tools.add("web_fetch")
```

Steps to Reproduce

1. Set a workspace path in the UI.
2. Enable Shell Access and/or Web Search.
3. Send a short or vague message: "help me", "what do we have here", "let's get started".
4. The agent responds that it has no access to `bash`, `python`, or `web_search`.

Notes

PR #4398 (merged 2026-06-16) fixed the structurally identical problem for scheduled task agents. This fix follows the same pattern.

Bash/python verified. Web search/web_fetch unverified — issue remains open until confirmed.

[jdmanring]

Verified working: agent now correctly offers bash and python on low-signal turns when Shell Access is enabled and a workspace is active.

[jdmanring]

Superseded by upstream PR #4366 (fix(agent): keep core tools available on low-signal rounds), which pins bash, python, web_search, web_fetch, read_file, write_file, and edit_file to ALWAYS_AVAILABLE system-wide — a broader and cleaner fix than the workspace-fast-path approach here. A temporary fork commit applies the same change to develop until #4366 merges through the ingest pipeline.

[jdmanring]

Reopening: closed as COMPLETED when the fix landed on develop, but per the fork rule an upstream-candidate issue stays OPEN until its upstream PR is filed — and nothing has been filed upstream yet. The staged branch is the active tracker until the PR goes up.