docs(workflow,agents): remove 'large files are bad' propaganda; add naming rule

The user called out the LLM training data bias: 'small files are
good, large files are bad.' This is wrong for production codebases.
Unreal has 15K+ line files; OS kernels, game engines, compilers all
routinely have 10K+ line files. File size is a non-issue. Cognitive
load is managed via naming, regions, and navigation tools (the
manual-slop MCP) — NOT via file splitting.

Updates:

1. AGENTS.md (master agent guidance):
   - Added 'File Size and Naming Convention' section
   - Added the hard rule: 'New namespaced src/<thing>.py files may
     only be created on the user's explicit request. If you find
     yourself about to create one, ASK FIRST.'
   - Defaults: helpers and sub-systems go in the parent module

2. conductor/workflow.md (Guiding Principles):
   - Removed 'Do NOT perform large file writes directamente' from
     principle 7 (it was a delegating rule, but 'large file writes'
     carried the propaganda)
   - Added principle 8: 'File Naming Convention (HARD RULE)' that
     references AGENTS.md
   - Re-phrased principle 9 (Research-First) to clarify it's about
     navigation efficiency, not file size

3. conductor/code_styleguides/python.md:
   - Removed the 'extremely large files that violate the Anti-OOP
     rule by necessity' framing
   - Added the new rule about new src/<thing>.py files

4. .opencode/agents/tier3-worker.md and .opencode/agents/tier4-qa.md:
   - Re-phrased 'Do NOT read full large files' to 'Use skeleton
     tools to navigate any file regardless of size. File size is
     not a concern; the right tools are.'
   - Added the new rule about not creating new src/<thing>.py
     files unless user explicitly requests it

5. conductor/tracks/qwen_llama_grok_followup_20260611/plan.md:
   - Updated the 'Naming Convention' section to reference the new
     'user explicit request' rule

This is docs-only. No code changes. The rule is now codified:
agents must ASK FIRST before creating new top-level src/ files.

conductor/code_styleguides/python.md

@@ -198,7 +198,11 @@ To minimize token usage and enhance visual scanning for human reviewers, heavily
 
 ## 14. Logical Region Blocks
 
-For extremely large files that violate the "Anti-OOP" rule by necessity (e.g., `App` class holding global UI state), use `#region: Section Name` and `#endregion: Section Name` tags (or `# --- Section Name ---` for visual grouping) to strictly organize methods and state properties. This establishes a predictable structure that MCP tools and agents can leverage for contextual masking.
+For files where many related methods/properties live in a single class (e.g., the `App` class in `src/gui_2.py` holding global UI state; the `src/ai_client.py` module holding 8 vendor entry points and supporting machinery), use `#region: Section Name` and `#endregion: Section Name` tags (or `# --- Section Name ---` for visual grouping) to strictly organize methods and state properties. This establishes a predictable structure that MCP tools and agents can leverage for contextual masking.
+
+**Removed anti-pattern (2026-06-11):** the prior version of this section said "extremely large files that violate the Anti-OOP rule by necessity." That framing was wrong. Files are not "large" in any absolute sense; production codebases (Unreal, OS kernels, game engines) routinely have 10K+ line files. The "Anti-OOP" rule is about data-vs-behavior separation, not file size. The `App` class in `src/gui_2.py` is not "violating" anything by being large; it's the natural shape of a class that owns the GUI orchestration. The `#region` convention is for navigability, not as a workaround for "files that got too big."
+
+**Hard rule on new `src/<thing>.py` files (added 2026-06-11):** New namespaced `src/<thing>.py` files may only be created on the user's explicit request. If you find yourself about to create one, ASK FIRST — don't just create it. Rationale: the user is the only one who can authorize a new top-level namespace. Defaults: helpers and sub-systems go in the parent module. E.g., AI-client-specific helpers go in `src/ai_client.py`; app-controller helpers go in `src/app_controller.py`; MCP-client helpers go in `src/mcp_client.py`. Even if the parent file is already 3K+ lines, the helper still goes there. If a new top-level `src/<thing>.py` is genuinely warranted (e.g., a truly new system that doesn't fit any existing parent), propose it in the next checkpoint or status note and wait for the user's explicit "yes, create it." See `AGENTS.md` "File Size and Naming Convention" for the full rule.
 
 ## 15. Modular Controller Pattern