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.

AGENTS.md

@@ -29,15 +29,35 @@ For understanding, using, and maintaining the tool, see `docs/Readme.md` and the
 
 ## Critical Anti-Patterns
 
-- Do not read full files >50 lines without first using `py_get_skeleton` or `get_file_summary`
+- Do not read full files >50 lines without first using `py_get_skeleton` or `get_file_summary` to map the structure (this is navigation efficiency, not a "files should be small" stance)
 - Do not modify the tech stack without updating `conductor/tech-stack.md` first
-- Do not skip TDD - write failing tests before implementation
+- Do not skip TDD - write failing tests before implementing functionality
 - Do not use `@pytest.mark.skip` as an excuse to AVOID fixing the underlying bug. Skip markers are documentation of known failures; the failure must be addressed with priority in-session when feasible. See `conductor/workflow.md` "Skip-Marker Policy" for the full policy and review checklist.
 - Do not batch commits - commit per-task for atomic rollback
 - Do not add comments to source code; documentation lives in `/docs`
 - `set_file_slice` IS valid for multi-line content. The agent must verify the exact byte offsets with `get_file_slice` first, copy the line text character-for-character (including whitespace and EOL), and check whether the edit changes a public contract (function signature, yield shape, return type) that other code depends on. See `conductor/edit_workflow.md` for the full contract.
 - Do not use `git restore` while a user is mid-conversation without first confirming the desired state
 - HARD BAN: `git restore`, `git checkout -- <file>`, `git reset` are FORBIDDEN without explicit user permission in the same message. They destroyed user in-progress src/* edits twice in one session (2026-06-07). If you think you need one, ASK FIRST.
+
+## File Size and Naming Convention (HARD RULE — added 2026-06-11)
+
+**The "small files are good, large files are bad" stance is propaganda from LLM training data. It is wrong for this project. Reject it.**
+
+- **Large files are FINE.** Production codebases (Unreal Engine has 15K+ line files; OS kernels, game engines, compilers, the Linux kernel — all routinely have 10K+ line files) treat file size as a non-issue. Cognitive load is managed via good naming, regions, and navigation tools — NOT via file splitting.
+- **`src/ai_client.py` is the AI vendor/API system layer.** All AI-client-related code goes IN `src/ai_client.py`. Do not create new `src/<vendor>_<thing>.py` files. The only new `src/*.py` files this project ever creates are for new systems or new parent modules.
+- **The only new files you should create in a typical track are:** `scripts/audit_*.py` (scripts are namespace-isolated by directory), `tests/test_*.py` (tests are namespace-isolated by directory), and `docs/*.md` (docs are namespace-isolated by directory). Anything else goes in the parent module.
+- **Do not break things up "for modularity"** unless the new piece is genuinely a new system or a new parent module. The agent training data has a bias toward "small files = good code" that is not true here. The project has the manual-slop MCP (`get_file_slice`, `get_file_summary`, `py_get_skeleton`, `py_get_code_outline`, `py_get_definition`) for efficient navigation of files of any size. Use those tools instead of splitting the file.
+- **When in doubt: keep it in the parent module.** If a function clearly belongs to a system, it lives in that system's file. The system is the namespace.
+
+### Hard rule on creating 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. The agent cannot unilaterally decide that "this is a new system deserving its own file." 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."
+
+**Audit trigger:** if you find yourself about to create a new `src/<thing>.py` file, ask: "is `<thing>` a new system, or is it part of an existing system?" If it's part of an existing system, the file goes in that system's file (e.g., `src/ai_client.py`, `src/app_controller.py`, `src/mcp_client.py`, etc.). If it's a new system, ASK THE USER before creating the file.
 - No giant edits: if your `manual-slop_edit_file` `new_string` exceeds ~20 lines, STOP and split it.
 - No diagnostic noise in production code. `sys.stderr.write(f"[XYZ_DIAG] ...")` lines added to `src/*.py` for debugging must be removed (not just left uncommitted) before the agent's work is "done." Diagnostic code that ships is technical debt. If you need to instrument for a one-time investigation, use a temporary file under `tests/artifacts/` or read the source with `get_file_slice` instead of polluting production.
 - No loop, no scope-creep, no report-instead-of-fix. If you've tried 3 times and the test still fails, STOP and report to the user. Do not write a 200-line status report as a substitute for the fix. Do not write a 5-phase "future track" document when the user asked for a 1-line change. See `conductor/workflow.md` "Process Anti-Patterns" for the full ruleset.