chore: add .mindmodel/ project constraints and conventions

Generated mindmodel covering stack, architecture, domain glossary,
coding conventions, DuckDB/requests/embeddings/error-handling patterns,
anti-patterns, and explicit constraints for naming, imports, DB access,
error handling, and testing.

.mindmodel/constraints/db_connection.yaml

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+# DB connection handling constraints
+
+rules:
+  - name: use_context_managers_for_connections
+    rule: "Prefer using 'with duckdb.connect(path, read_only=...) as conn' for scoped DB interactions where possible."
+    rationale: "Ensures proper resource cleanup and avoids connection leaks."
+
+  - name: read_only_for_compute
+    rule: "Use read_only=True for compute steps that only read data (SVD, similarity compute)."
+    rationale: "Allows safe parallel workers and reduces write contention."
+
+  - name: short_lived_writes
+    rule: "When performing database writes, open short-lived connections, commit quickly and close."
+    rationale: "Avoids long-lived transactions and reduces lock windows."
+
+examples:
+  - path: pipeline/svd_pipeline.py
+    snippet: |
+      conn = duckdb.connect(db_path, read_only=True)
+      try:
+          rows = conn.execute(...).fetchall()
+      finally:
+          conn.close()
+
+anti_patterns_and_remediations:
+  - bad: "Creating a global connection at import that performs migrations."
+    remediation: "Move migrations to an explicit init function that runs at deployment/upgrade time."
+  - bad: "Not closing connections on exceptions."
+    remediation: "Wrap connects in `with` or finally: conn.close() blocks."

.mindmodel/constraints/error_handling.yaml

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+# Error handling style rules (YAML constraint example)
+
+rules:
+  - name: explicit_exceptions
+    rule: "Raise explicit exceptions (ValueError, ProviderError) for known error conditions rather than returning magic values."
+    examples:
+      - good: |
+          if not isinstance(text, str):
+              raise ProviderError('text must be a string')
+      - bad: |
+          if not isinstance(text, str):
+              return []
+
+  - name: avoid_broad_except
+    rule: "Avoid 'except Exception:' that swallows errors. If broad except is used for best-effort, log the exception with logger.exception and re-raise or convert."
+    examples:
+      - bad: |
+          try:
+              do_work()
+          except Exception:
+              return []
+      - remediation: |
+          try:
+              do_work()
+          except SpecificError as exc:
+              logger.warning('Handled error: %s', exc)
+              raise
+
+  - name: logging_over_print
+    rule: "Prefer logger.* over print() for messages and errors."
+    examples:
+      - bad: "print('Error fetching motions from API: %s' % e)"
+      - good: "logger.exception('Error fetching motions from API')"
+
+enforcement_examples:
+  - "Add a static code check to flag 'print(' in modules (except in simple scripts) and 'except Exception:' usages without logger.exception."

.mindmodel/constraints/imports.yaml

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+# Import grouping and ordering constraints
+
+rules:
+  - name: grouping
+    rule: "Group imports in three sections separated by a single blank line: stdlib, third-party, local."
+    examples:
+      - good: |
+          import json
+          import logging
+
+          import requests
+          import duckdb
+
+          from .pipeline import text_pipeline
+      - bad: |
+          import duckdb
+          import json
+          from pipeline import text_pipeline
+
+  - name: from_imports
+    rule: "Prefer 'from x import y' only when it improves clarity or avoids circular import; otherwise import module and reference attributes."
+
+enforcement_examples:
+  - "Run isort or ruff- import sorting in pre-commit or CI to enforce ordering."

.mindmodel/constraints/naming.yaml

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+# Naming constraint rules (example constraint file)
+
+rules:
+  - name: module_file_names
+    rule: "Use snake_case for Python module filenames (e.g., text_pipeline.py, ai_provider.py)."
+    examples:
+      - good: "text_pipeline.py"
+      - bad: "TextPipeline.py"
+
+  - name: function_names
+    rule: "Use snake_case for functions and methods."
+    examples:
+      - good: "def compute_similarities(...):"
+      - bad: "def ComputeSimilarities(...):"
+
+  - name: class_names
+    rule: "Use PascalCase for classes."
+    examples:
+      - good: "class MotionDatabase:"
+      - bad: "class motion_database:"
+
+  - name: constants
+    rule: "Constants use UPPER_SNAKE_CASE."
+    examples:
+      - good: "VOTE_MAP = { ... }"
+      - bad: "vote_map = { ... }"
+
+enforcement_examples:
+  - "Add a linter rule in CI: ruff or flake8 naming plugin to detect violations."
+  - "Run `python -m pip install ruff` and `ruff check` as part of CI."

.mindmodel/constraints/testing.yaml

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+# Testing conventions constraint (YAML)
+
+rules:
+  - name: test_naming
+    rule: "Use pytest and name tests test_*.py and test_* functions."
+    examples:
+      - good: "tests/test_text_pipeline.py"
+      - bad: "tests/text_pipeline_test.py"
+
+  - name: fixtures_and_conftest
+    rule: "Place shared fixtures in tests/conftest.py or tests/fixtures/ for reuse."
+    examples:
+      - good: "use fixtures declared in tests/conftest.py"
+
+  - name: assert_raises
+    rule: "Explicitly assert expected exceptions with pytest.raises for invalid input."
+    examples:
+      - good: |
+          import pytest
+
+          def test_invalid_input():
+              with pytest.raises(ValueError):
+                  function_under_test('bad')
+
+enforcement_examples:
+  - "Run pytest in CI; fail if tests don't run or if there are regressions."