docs: add AGENTS.md rules, CLAUDE.md import

AGENTS.md

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+# Agent rules for dbmole-mcp
+
+Applies to every change in this repo, by any agent or human.
+
+## Code style
+
+- 4-space indentation
+- No semicolons where possible (`semicolons: asNeeded`)
+- Single quotes where possible
+- Functions as `const fn = () => {}` where possible
+- No trailing commas before a closing `}`, `]`, `)` (`trailingCommas: none`)
+- Biome enforces all of the above — run `npm run lint:fix` before every commit
+- Line width 100
+
+## TypeScript discipline
+
+- No `as unknown as X` double-casts anywhere
+- No `@ts-ignore` / `@ts-expect-error` / `any` in `src/`
+- In tests prefer typed fakes (see `test/unit/helpers.ts`); a single `as` cast is
+  a last resort, only when there is genuinely no typed way
+- Types must line up by construction — if they don't, fix the design, not the cast
+
+## Testing
+
+- TDD: write the failing test first, watch it fail, implement, watch it pass
+- Full coverage: unit tests (mocked IO) + integration tests via testcontainers
+- Coverage thresholds ≥90% lines/functions on the unit project — never lower them
+- `npm run test:unit` (fast), `npm run test:int` (needs Docker)
+
+## Commits
+
+- Conventional Commits: `<type>(<scope>): <imperative summary>`
+- Subject ≤50 chars (hard cap 72), no trailing period
+- Body only when the *why* is not obvious from the diff; wrap at 72
+- NO AI attribution: no `Co-Authored-By: Claude ...`, no "Generated with ..."
+- No emoji
+
+## Project constraints
+
+- stdout is the MCP protocol channel — diagnostics go to `console.error` ONLY,
+  never `console.log`
+- ESM with NodeNext resolution: relative imports need the `.js` extension
+- MCP SDK v1 (`@modelcontextprotocol/sdk`): `registerTool` takes a ZodRawShape
+  (plain object of zod fields), NOT `z.object()`; subpath imports
+  (`server/mcp.js`, `server/stdio.js`, `client/index.js`, `inMemory.js`, `types.js`)
+- zod 3 (`import * as z from 'zod'`)

CLAUDE.md

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+@AGENTS.md