chore: implement local quality foundation

CONTRIBUTING.md

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+# Contributing
+
+## Daily Workflow
+
+Use this command surface:
+
+1. `pnpm setup` (once per machine)
+2. `pnpm dev` (daily coding loop)
+3. `pnpm verify` (before push)
+
+Optional:
+
+1. `pnpm quick` (faster checks while coding)
+2. `pnpm verify:strict` (aspirational strict gate while we burn down baseline debt)
+3. `pnpm guide` (show command reference)
+
+## Quality Gates
+
+Before opening or updating a PR:
+
+1. `pnpm verify` must pass
+2. `pnpm verify:strict` is currently optional until formatting and full client typecheck baseline debt is reduced.
+3. If tests touched critical flows, run `pnpm test:e2e:smoke`
+4. If coverage-sensitive changes are made, run `pnpm coverage`
+
+## Check vs Fix Commands
+
+Non-mutating:
+
+1. `pnpm format:check`
+2. `pnpm lint:check`
+3. `pnpm typecheck`
+4. `pnpm typecheck:full`
+5. `pnpm typecheck:client:baseline:update` (update accepted client TS baseline after intentional changes)
+
+Mutating:
+
+1. `pnpm format`
+2. `pnpm lint:fix`
+
+## Database Commands
+
+1. `pnpm db:up`
+2. `pnpm db:migrate`
+3. `pnpm db:seed`
+4. `pnpm db:reset`
+
+## Troubleshooting
+
+1. Run `pnpm doctor` for environment checks.
+2. If dependencies changed, run `pnpm install`.
+3. If local DB state is inconsistent, run `pnpm db:reset`.