fix: remove stale generated files and improve type generation infrastructure

This commit addresses the downstream report that pricing options were missing
the is_fixed discriminator field. Investigation revealed the discriminator
already exists in the individual pricing option schema files generated by
datamodel-code-generator.

The root causes were:
1. Stale files (pricing_option.py, brand_manifest_ref.py, index.py, start_timing.py)
   persisting from previous generations
2. No mechanism to clean output directory before regeneration
3. Timestamp-only changes creating noisy commits

Changes:
- Remove stale generated files that no longer correspond to current schemas
- Add clean slate generation: delete entire output directory before regenerating
  types to prevent stale artifacts from old schema versions
- Add timestamp change detection: restore files where only the generation
  timestamp changed to avoid noisy commits
- Update CLAUDE.md with patterns for preventing stale files and noisy commits

All pricing options now correctly have the is_fixed discriminator:
- Fixed-rate: CpmFixedRatePricingOption, VcpmFixedRatePricingOption, etc.
  (is_fixed: Annotated[Literal[True], ...])
- Auction: CpmAuctionPricingOption, VcpmAuctionPricingOption
  (is_fixed: Annotated[Literal[False], ...])

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: bokelley

CLAUDE.md

@@ -27,6 +27,14 @@ Files in `src/adcp/types/generated_poc/` and `src/adcp/types/generated.py` are a
 
 We use `scripts/post_generate_fixes.py` which runs automatically after type generation to apply necessary modifications that can't be generated.
 
+**Preventing Stale Files:**
+
+The generation script (`scripts/generate_types.py`) **deletes the entire output directory** before regenerating types. This prevents stale files from persisting when schemas are renamed or removed. Without this, old generated files could remain checked in indefinitely, causing import errors and confusion about which types are actually current.
+
+**Avoiding Noisy Commits:**
+
+After generation, the script automatically restores files where only the timestamp changed (e.g., `#   timestamp: 2025-11-18T03:32:03+00:00`). This prevents commits with 100+ file changes where the only difference is the generation timestamp, making actual changes easier to review.
+
 **Type Name Collisions:**
 
 The upstream AdCP schemas define multiple types with the same name (e.g., `Contact`, `Asset`, `Status`) in different schema files. These are **genuinely different types** with different fields, not duplicates.
@@ -59,6 +67,14 @@ from adcp.types.generated_poc.format import Asset as FormatAsset
    - `create_media_buy_request.py`
    - `get_products_request.py`
 
+**Note on Pricing Options:**
+
+The code generator creates individual files for each pricing option (e.g., `cpm_fixed_option.py`, `cpm_auction_option.py`) with the `is_fixed` discriminator field already included:
+- Fixed-rate options: `is_fixed: Annotated[Literal[True], ...]`
+- Auction options: `is_fixed: Annotated[Literal[False], ...]`
+
+These are used via union types in `Product.pricing_options`. No post-generation fix is needed for pricing options.
+
 **To add new post-generation fixes:**
 Edit `scripts/post_generate_fixes.py` and add a new function. The script:
 - Runs automatically via `generate_types.py`

scripts/generate_types.py

@@ -179,6 +179,76 @@ def generate_types(input_dir: Path):
     return True
 
 
+def normalize_timestamp(content: str) -> str:
+    """Remove timestamp from generated file for comparison.
+
+    Timestamps look like:
+    #   timestamp: 2025-11-18T03:32:03+00:00
+    """
+    return re.sub(r"#\s+timestamp:.*\n", "", content)
+
+
+def restore_unchanged_files():
+    """Restore files where only the timestamp changed.
+
+    This prevents noisy commits where the only change is the generation timestamp.
+    We compare file contents ignoring timestamp lines.
+    """
+    print("Checking for timestamp-only changes...")
+
+    # Get git status to see modified files
+    result = subprocess.run(
+        ["git", "diff", "--name-only", str(OUTPUT_DIR)],
+        capture_output=True,
+        text=True,
+        cwd=REPO_ROOT,
+    )
+
+    if result.returncode != 0:
+        print("  Could not check git status (skipping restoration)")
+        return
+
+    modified_files = [f for f in result.stdout.strip().split("\n") if f]
+    restored_count = 0
+
+    for rel_path in modified_files:
+        file_path = REPO_ROOT / rel_path
+        if not file_path.exists():
+            continue
+
+        # Get current (new) content
+        with open(file_path) as f:
+            new_content = f.read()
+
+        # Get old content from git
+        git_result = subprocess.run(
+            ["git", "show", f"HEAD:{rel_path}"],
+            capture_output=True,
+            text=True,
+            cwd=REPO_ROOT,
+        )
+
+        if git_result.returncode != 0:
+            continue
+
+        old_content = git_result.stdout
+
+        # Compare without timestamps
+        if normalize_timestamp(old_content) == normalize_timestamp(new_content):
+            # Only timestamp changed, restore old version
+            subprocess.run(
+                ["git", "checkout", "HEAD", "--", rel_path],
+                cwd=REPO_ROOT,
+                capture_output=True,
+            )
+            restored_count += 1
+
+    if restored_count > 0:
+        print(f"  ✓ Restored {restored_count} file(s) with only timestamp changes")
+    else:
+        print("  No timestamp-only changes found")
+
+
 def apply_post_generation_fixes():
     """Apply post-generation fixes using the dedicated script."""
     print("Running post-generation fixes...")
@@ -211,6 +281,13 @@ def main():
 
     temp_schemas = None
     try:
+        # Clean output directory to prevent stale files
+        # This ensures old/renamed schema files don't persist
+        if OUTPUT_DIR.exists():
+            print("Cleaning output directory...")
+            shutil.rmtree(OUTPUT_DIR)
+            print("  ✓ Removed stale generated files\n")
+
         # Ensure output directory exists
         OUTPUT_DIR.mkdir(parents=True, exist_ok=True)
 
@@ -228,6 +305,9 @@ def main():
         if not apply_post_generation_fixes():
             return 1
 
+        # Restore files where only timestamp changed
+        restore_unchanged_files()
+
         # Count generated files
         py_files = list(OUTPUT_DIR.glob("*.py"))
         print("\n✓ Successfully generated types")

src/adcp/types/generated_poc/__init__.py

@@ -1,3 +1,3 @@
 # generated by datamodel-codegen:
 #   filename:  .schema_temp
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00

src/adcp/types/generated_poc/activate_signal_request.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  activate-signal-request.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/activate_signal_response.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  activate-signal-response.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/activation_key.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  activation-key.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/adagents.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  adagents.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/asset_type.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  asset-type.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/audio_asset.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  audio-asset.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations
 

src/adcp/types/generated_poc/brand_manifest.py

@@ -1,6 +1,6 @@
 # generated by datamodel-codegen:
 #   filename:  brand-manifest.json
-#   timestamp: 2025-11-18T03:04:10+00:00
+#   timestamp: 2025-11-18T03:35:10+00:00
 
 from __future__ import annotations