feat: initial Postgres From Zero companion repo

Companion to the Coursera course "Postgres From Zero", sibling to
paiml/mysql-from-zero and paiml/duckdb-from-zero. A single
`git clone && make demo` away from running every example shown in
the videos plus the Rust capstone foundation.

Layout:
- sql/01-fundamentals + sql/02-joins: 8 SQL examples covering connect,
  list tables, modify, export, join traversal, INNER vs LEFT, and
  EXPLAIN (ANALYZE, BUFFERS).
- sql/pagila-analytics: the queries the Rust capstone runs.
- crates/postgres-reports: sqlx::PgPool + clap CLI with 13 named
  provable contracts asserted at runtime; lib + bin split so the
  capstone reading can extend the lib API directly.
- scripts/load-pagila.sh: idempotent Pagila loader (Sakila port for
  Postgres). scripts/verify.sh asserts all four headline counts.
- docker-compose.yml: postgres:16 with persistent pgdata volume.

Provable contracts (contracts/postgres-reports.yaml is the manifest):
  customers-row-count, customers-top-nonzero, customers-monotonic,
  customers-row-shape, films-row-count, films-top-nonzero,
  films-monotonic, films-row-shape, actors-row-count,
  actors-top-nonzero, actors-monotonic, actors-row-shape,
  run-output. Each is asserted at runtime, prints
  `contract: <name> OK` to stderr on success, and has a per-contract
  unit test (positive + #[should_panic] negative).

Quality status:
  - 45 tests passing (27 unit + 7 binary smoke + 6 integration + 5 doctest)
  - 100% line coverage / 100% function coverage (cargo llvm-cov gate)
  - cargo clippy --all-targets -- -D warnings clean (workspace lints
    in Cargo.toml + .clippy.toml in effect)
  - pmat quality-gate: 1 violation (entropy false-positive on small
    repos, matches duckdb-from-zero baseline)
  - Criterion bench for assertion overhead (~7 ns/row, linear scaling)

Compliance scaffold: LICENSE (MIT), CHANGELOG.md, deny.toml,
.clippy.toml, .cargo/config.toml, [workspace.lints.{rust,clippy}],
release profile (lto = "thin", codegen-units = 1, strip = "symbols").

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: noahgift

.cargo/config.toml

@@ -0,0 +1,9 @@
+[build]
+# Match the sibling companion repos for reproducible builds.
+
+[net]
+retry = 3
+git-fetch-with-cli = true
+
+[term]
+verbose = false

.clippy.toml

@@ -0,0 +1,3 @@
+disallowed-methods = [
+    { path = "std::env::set_var", reason = "process-global state breaks parallel tests" },
+]

.env.example

@@ -0,0 +1 @@
+DATABASE_URL=postgres://postgres:postgres@localhost:5432/pagila

.gitignore

@@ -0,0 +1,10 @@
+/target/
+.env
+/data/
+*.dump
+.DS_Store
+
+# Local pmat / pv tooling state
+/.pmat/
+/.pmat-metrics/
+/.pv/

CHANGELOG.md

@@ -0,0 +1,26 @@
+# Changelog
+
+All notable changes to this companion repo are recorded here. The format
+follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and the repo
+follows [Semantic Versioning](https://semver.org/) for the Rust crate
+(`postgres-reports`); the SQL examples and Makefile entry points are
+versioned together as a single repo.
+
+## [Unreleased]
+
+### Added
+- `make verify` headline-count smoke test (film/actor/rental/language)
+- `make demo` SQL walkthrough across `sql/01-fundamentals/` and `sql/02-joins/`
+- `make capstone` entry point that runs `postgres-reports` against Pagila
+- `make coverage` cargo-llvm-cov gate with a 100% line floor
+- `crates/postgres-reports/` with `sqlx::PgPool`, clap CLI, and 13 named
+  provable contracts asserted at runtime
+- `contracts/postgres-reports.yaml` machine-readable contract index
+- `docker-compose.yml` for `postgres:16` with a persistent `pgdata` volume
+- `scripts/load-pagila.sh` idempotent loader
+
+## [0.1.0] - 2026-05-05
+
+Initial public release. Companion repo for the Coursera course
+**Postgres From Zero**, sibling to `paiml/mysql-from-zero` and
+`paiml/duckdb-from-zero`.