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-valkey/README.md

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+# wfe-valkey
+
+Valkey (Redis-compatible) provider for distributed locking, queues, and lifecycle events in WFE.
+
+## What it does
+
+Provides three provider implementations backed by Valkey (or any Redis-compatible server) using the `redis` crate with multiplexed async connections. Handles distributed lock coordination across multiple WFE host instances, work queue distribution for workflows/events/indexing, and pub/sub lifecycle event broadcasting.
+
+## Quick start
+
+```rust
+use wfe_valkey::{ValkeyLockProvider, ValkeyQueueProvider, ValkeyLifecyclePublisher};
+
+let redis_url = "redis://127.0.0.1:6379";
+let prefix = "wfe"; // key prefix for namespacing
+
+let locks = ValkeyLockProvider::new(redis_url, prefix).await?;
+let queues = ValkeyQueueProvider::new(redis_url, prefix).await?;
+let lifecycle = ValkeyLifecyclePublisher::new(redis_url, prefix).await?;
+```
+
+Custom lock duration (default is 30 seconds):
+
+```rust
+use std::time::Duration;
+
+let locks = ValkeyLockProvider::new(redis_url, prefix).await?
+    .with_lock_duration(Duration::from_secs(10));
+```
+
+## API
+
+| Type | Trait | Purpose |
+|------|-------|---------|
+| `ValkeyLockProvider` | `DistributedLockProvider` | Distributed mutex via `SET NX EX`. Release uses a Lua script to ensure only the holder can unlock. |
+| `ValkeyQueueProvider` | `QueueProvider` | FIFO work queues via `LPUSH`/`RPOP`. Separate queues for `Workflow`, `Event`, and `Index` work types. |
+| `ValkeyLifecyclePublisher` | `LifecyclePublisher` | Pub/sub lifecycle events. Publishes to both an instance-specific channel and a global `all` channel. |
+
+### Key layout
+
+All keys are prefixed with the configured prefix (e.g., `wfe`):
+
+| Pattern | Usage |
+|---------|-------|
+| `{prefix}:lock:{resource}` | Distributed lock for a resource |
+| `{prefix}:queue:workflow` | Workflow processing queue |
+| `{prefix}:queue:event` | Event processing queue |
+| `{prefix}:queue:index` | Index update queue |
+| `{prefix}:lifecycle:{workflow_id}` | Lifecycle events for a specific workflow |
+| `{prefix}:lifecycle:all` | All lifecycle events |
+
+## Configuration
+
+Connection string is a standard Redis URI:
+
+```
+redis://127.0.0.1:6379
+redis://:password@host:6379/0
+```
+
+Each provider creates its own multiplexed connection. The prefix parameter namespaces all keys, so multiple WFE deployments can share a single Valkey instance.
+
+## Testing
+
+Requires a running Valkey instance. Use the project docker-compose:
+
+```sh
+docker compose up -d valkey
+cargo test -p wfe-valkey
+```
+
+Default test connection: `redis://127.0.0.1:6379`
+
+## License
+
+MIT