refactor(paths): replace 26 modules hardcoded ~/.pry/ with PRY_DATA_DIR

Each module did:
    X_DIR = Path(os.path.expanduser("~/.pry/x"))

After:
    from paths import PRY_DATA_DIR
    X_DIR = PRY_DATA_DIR / "x"

The module-level Path construction is preserved, so the rest of the
code is unchanged. PRY_DATA_DIR is read once at import (overridable via
the env var of the same name).

Verified:
- 407 tests collect (was 5 collection errors from a misplaced import)
- 83 sampled tests pass (intelligence, proxy_manager, x402, agency,
  gdpr, referrals, marketplace, api)
- 0 remaining hardcoded ~/.pry references in .py files

Follow-up: paths.py adds subdir(name) helper for new code that wants
auto-mkdir; existing modules still call .mkdir(exist_ok=True) themselves
to preserve the eager-init behavior they had before.

llm_providers/registry.py

@@ -16,9 +16,10 @@ from typing import Any
 
 from llm_providers.base import LLMProvider, LLMResponse, ReferralConfig
 
+from paths import PRY_DATA_DIR
 logger = logging.getLogger(__name__)
 
-USAGE_DIR = Path(os.path.expanduser("~/.pry/llm_usage"))
+USAGE_DIR = PRY_DATA_DIR / "llm_usage"
 USAGE_DIR.mkdir(parents=True, exist_ok=True)