docs: add README for workspace and all 7 crates

Root README covers architecture, Rust builder API quick start,
YAML pipeline quick start, provider table, deno executor overview,
feature flags, and testing instructions.

Per-crate READMEs follow consistent structure: one-liner, what it
does, quick start code example, API reference, configuration,
testing, license. Engineering-confident tone throughout.

wfe-sqlite/README.md

@@ -0,0 +1,67 @@
+# wfe-sqlite
+
+SQLite persistence provider for the WFE workflow engine.
+
+## What it does
+
+Implements the full `PersistenceProvider` trait (workflows, events, subscriptions, scheduled commands, execution errors) backed by SQLite via sqlx. Supports both in-memory and file-based databases. Tables and indexes are created automatically on startup -- no migrations to run.
+
+## Quick start
+
+```rust
+use wfe_sqlite::SqlitePersistenceProvider;
+
+// In-memory (good for tests and single-process deployments)
+let provider = SqlitePersistenceProvider::new(":memory:").await?;
+
+// File-based (persistent across restarts)
+let provider = SqlitePersistenceProvider::new("sqlite:///tmp/wfe.db").await?;
+```
+
+Wire it into the WFE host as your persistence layer:
+
+```rust
+let host = WorkflowHost::new(provider);
+```
+
+## API
+
+| Type | Trait |
+|------|-------|
+| `SqlitePersistenceProvider` | `PersistenceProvider`, `WorkflowRepository`, `EventRepository`, `SubscriptionRepository`, `ScheduledCommandRepository` |
+
+Key methods come from the traits -- `create_new_workflow`, `persist_workflow`, `get_runnable_instances`, `create_event`, `schedule_command`, and so on. See `wfe-core` for the full trait definitions.
+
+## Configuration
+
+The constructor takes a standard SQLite connection string:
+
+| Value | Behavior |
+|-------|----------|
+| `":memory:"` | In-memory database, single connection, lost on drop |
+| `"sqlite:///path/to/db"` | File-backed, WAL journal mode, up to 4 connections |
+
+WAL mode and foreign keys are enabled automatically. For in-memory mode, the pool is capped at 1 connection to avoid separate database instances.
+
+## Schema
+
+Six tables are created in the default schema:
+
+- `workflows` -- workflow instance state and metadata
+- `execution_pointers` -- step execution state, linked to workflows via foreign key
+- `events` -- published events pending processing
+- `event_subscriptions` -- active event subscriptions with CAS-style token locking
+- `scheduled_commands` -- deferred commands with dedup on `(command_name, data)`
+- `execution_errors` -- error log for failed step executions
+
+## Testing
+
+No external dependencies required. Tests run against `:memory:`:
+
+```sh
+cargo test -p wfe-sqlite
+```
+
+## License
+
+MIT