docs: add python client readme

clients/ember-py/README.md

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+# ember-py
+
+python gRPC client for the [ember](https://github.com/kacy/ember) cache server.
+
+## installation
+
+```bash
+pip install ember-py
+```
+
+or install from source:
+
+```bash
+cd clients/ember-py
+pip install .
+```
+
+for development (includes grpc tools and pytest):
+
+```bash
+pip install -e ".[dev]"
+```
+
+## quickstart
+
+```python
+from ember import EmberClient
+
+client = EmberClient("localhost:6380")
+client.set("greeting", b"hello world")
+
+value = client.get("greeting")
+print(value)  # b"hello world"
+
+client.close()
+```
+
+or use the context manager for automatic cleanup:
+
+```python
+with EmberClient("localhost:6380") as client:
+    client.set("counter", b"0")
+    client.incr("counter")
+    print(client.get("counter"))  # b"1"
+```
+
+## authentication
+
+pass a password to the client constructor. it's sent as gRPC metadata on every request.
+
+```python
+client = EmberClient("localhost:6380", password="secret")
+```
+
+## API reference
+
+### strings
+
+| method | description |
+|--------|-------------|
+| `get(key) -> bytes \| None` | get value by key |
+| `set(key, value, ex=None, px=None, nx=False, xx=False) -> bool` | set key-value pair |
+| `delete(*keys) -> int` | delete keys, returns count removed |
+| `exists(*keys) -> int` | count how many keys exist |
+| `incr(key) -> int` | increment by 1 |
+| `incr_by(key, delta) -> int` | increment by delta |
+| `expire(key, seconds) -> bool` | set TTL in seconds |
+| `ttl(key) -> int` | get remaining TTL (-1 = no expiry, -2 = not found) |
+
+### lists
+
+| method | description |
+|--------|-------------|
+| `lpush(key, *values) -> int` | prepend to list, returns new length |
+| `rpush(key, *values) -> int` | append to list, returns new length |
+| `lpop(key) -> bytes \| None` | pop from head |
+| `rpop(key) -> bytes \| None` | pop from tail |
+| `lrange(key, start, stop) -> list[bytes]` | get range of elements |
+| `llen(key) -> int` | get list length |
+
+### hashes
+
+| method | description |
+|--------|-------------|
+| `hset(key, fields) -> int` | set fields (dict), returns new field count |
+| `hget(key, field) -> bytes \| None` | get a single field |
+| `hgetall(key) -> dict[str, bytes]` | get all fields |
+| `hdel(key, *fields) -> int` | delete fields, returns count removed |
+
+### sets
+
+| method | description |
+|--------|-------------|
+| `sadd(key, *members) -> int` | add members, returns new member count |
+| `smembers(key) -> set[str]` | get all members |
+| `scard(key) -> int` | get set cardinality |
+
+### sorted sets
+
+| method | description |
+|--------|-------------|
+| `zadd(key, members) -> int` | add scored members (dict of member→score) |
+| `zrange(key, start, stop, with_scores=False) -> list[tuple]` | get range by rank |
+
+### vectors
+
+| method | description |
+|--------|-------------|
+| `vadd(key, element, vector, metric="cosine", m=16, ef=64) -> bool` | add vector to HNSW index |
+| `vsim(key, query, count=10, ef_search=None) -> list[tuple]` | kNN similarity search, returns (element, distance) pairs |
+
+vectors are sent as packed IEEE 754 floats over gRPC — no string parsing overhead compared to RESP.
+
+### server
+
+| method | description |
+|--------|-------------|
+| `ping() -> str` | health check, returns "PONG" |
+| `flushdb(async_mode=False)` | remove all keys |
+| `dbsize() -> int` | total key count |
+
+## connection details
+
+the gRPC server runs on port **6380** by default (separate from the RESP3 port 6379). start the ember server with gRPC enabled:
+
+```bash
+ember-server --grpc-port 6380
+```
+
+the client uses an insecure channel by default. TLS support can be configured at the server level.
+
+## development
+
+regenerate protobuf stubs after changing `proto/ember/v1/ember.proto`:
+
+```bash
+make proto-gen
+```
+
+run tests:
+
+```bash
+make test
+```
+
+install in editable mode with dev dependencies:
+
+```bash
+make install-dev
+```