chore(release): 0.0.3

Squash-merge lib-standardisation: adopt repo standards across packaging,
tooling, docs, and CI.

- standardize pyproject.toml (canonical packaging, lint config, extras, GSDFC pydoclint)
- add py.typed marker, modernize type hints and Google-style docstrings
- nest generated docs under docs/lib and docs/mcp; add hand-written wiki
- adopt standard Type A PyPI CI pipeline (tag==version guard + quality gate)
- promote generated CHANGELOG.md; bump version to 0.0.3

docs/mcp/modules/mail_intake.parsers.body.json

@@ -0,0 +1,23 @@
+{
+  "module": "mail_intake.parsers.body",
+  "content": {
+    "path": "mail_intake.parsers.body",
+    "docstring": "# Summary\n\nMessage body extraction utilities for Mail Intake.\n\nThis module contains helper functions for extracting a best-effort\nplain-text body from provider-native message payloads.\n\nThe logic is intentionally tolerant of malformed or partial data and\nprefers human-readable text over fidelity to original formatting.",
+    "objects": {
+      "MailIntakeParsingError": {
+        "name": "MailIntakeParsingError",
+        "kind": "class",
+        "path": "mail_intake.parsers.body.MailIntakeParsingError",
+        "signature": null,
+        "docstring": "Errors encountered while parsing message content.\n\nNotes:\n    **Lifecycle:**\n\n        - Raised when raw provider payloads cannot be interpreted or\n          normalized into internal domain models."
+      },
+      "extract_body": {
+        "name": "extract_body",
+        "kind": "function",
+        "path": "mail_intake.parsers.body.extract_body",
+        "signature": "extract_body(payload: dict[str, Any]) -> str",
+        "docstring": "Extract the best-effort message body from a Gmail payload.\n\nPriority:\n\n1. `text/plain`\n2. `text/html` (stripped to text)\n3. Single-part body\n4. Empty string (if nothing usable found)\n\nArgs:\n    payload (dict[str, Any]):\n        Provider-native message payload dictionary.\n\nReturns:\n    str:\n        Extracted plain-text message body."
+      }
+    }
+  }
+}