docs: add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+```bash
+make fmt              # gofmt + goimports
+make lint             # golangci-lint
+make vuln             # govulncheck
+make test             # run all module tests with -race
+make test-coverage    # generate coverage report in .coverage/
+make test-patch-coverage  # patch-only coverage vs origin/main
+make tools            # install all pinned dev tools
+make setup-hooks      # install dev tools + git hooks (lefthook + commitlint)
+make cli-smoke-build      # build the modkit CLI binary
+make cli-smoke-scaffold   # smoke test CLI scaffold flow
+```
+
+Run a single package's tests:
+```bash
+cd modkit/kernel && go test -race ./...
+```
+
+Run tests for all workspace modules (including examples):
+```bash
+# make test does this automatically by iterating all go.mod files
+make test
+```
+
+## Architecture
+
+modkit is a multi-module Go workspace (`go.work`). The root module is `github.com/go-modkit/modkit`. Examples are separate modules under `examples/`.
+
+```
+modkit/
+├── modkit/           # Core framework packages (the library)
+│   ├── module/       # Public API: ModuleDef, ProviderDef, Token, Resolver
+│   ├── kernel/       # Graph builder, visibility enforcer, lazy singleton container, bootstrap
+│   ├── http/         # Chi-based HTTP adapter: Router, RegisterRoutes, Serve, middleware
+│   ├── logging/      # Logger interface + slog adapter + nop
+│   ├── config/       # Typed env config module helpers
+│   ├── data/         # DB providers: sqlmodule (shared contract), postgres, sqlite sub-packages
+│   └── testkit/      # Test harness: bootstrap helpers, provider overrides
+├── examples/         # Runnable apps (separate go.mod each)
+│   ├── hello-simple/ # Minimal bootstrap, no Docker
+│   ├── hello-mysql/  # Full CRUD: auth, users, middleware, sqlc, swagger
+│   ├── hello-postgres/
+│   └── hello-sqlite/
+├── cmd/modkit/       # CLI tool (cobra): `modkit new app <name>`
+└── docs/             # Guides and architecture reference
+```
+
+### Bootstrap Flow
+
+`kernel.Bootstrap(rootModule)` does four things in order:
+
+1. **Build graph** — flattens the import tree depth-first, rejects cycles and duplicate names
+2. **Build visibility** — computes which tokens each module can access (own providers + exported tokens from imports)
+3. **Create container** — registers provider factory functions (not built yet)
+4. **Build controllers** — calls each `ControllerDef.Build`, which triggers lazy provider construction
+
+Providers are lazy singletons: built on first `Get()`, cached for subsequent calls.
+
+### Key Interfaces
+
+```go
+// A module must be a pointer and implement:
+type Module interface {
+    Definition() ModuleDef
+}
+
+// Controllers must implement to register HTTP routes:
+type RouteRegistrar interface {
+    RegisterRoutes(router Router)
+}
+
+// Resolve a typed dependency inside a Build function:
+svc, err := module.Get[T](r, "token.name")
+```
+
+### Token Naming Convention
+
+Tokens follow `"module.component"` — e.g., `"users.service"`, `"db.connection"`. Shared SQL contract tokens live in `sqlmodule`: `sqlmodule.TokenDB`, `sqlmodule.TokenDialect`.
+
+## Conventions
+
+- Modules must be **pointers** — pointer identity determines shared import deduplication
+- `Definition()` must be **pure/deterministic** — no mutable side effects or counters
+- Resolve deps via `r.Get()` inside `Build` functions; always check `err` before use
+- Controllers call explicit `r.Handle(method, path, handler)` — no reflection, no decorators
+- Error handling: return/wrap errors; no panic-driven control flow
+- Tests: `*_test.go` alongside implementation, table-driven where useful
+
+## Anti-Patterns
+
+- Do not add reflection or decorator magic to user-facing APIs
+- Do not make `Definition()` stateful
+- Do not wire across module boundaries without going through the export/import mechanism
+- Do not hand-edit generated files (`*.sql.go`, swagger-generated docs)
+
+## Branch and PR Workflow
+
+- `main` is integration-only — never commit directly on it
+- Create work on a worktree branch: `git worktree add .worktrees/<task> -b feat/<task> main`
+- Before opening a PR: `make fmt && make lint && make vuln && make test && make test-coverage`
+- If the repo has a PR template (`.github/pull_request_template.md`), follow it exactly and actively check/uncheck each item
+- Include `Resolves #<number>` lines for any GitHub issues the PR addresses
+- Commit messages follow Conventional Commits: `feat:`, `fix:`, `docs:`, `test:`, `chore:`, `refactor:`, `perf:`, `ci:` — header ≤80 characters