feat(server): add support for extra maps in adapter configuration

* Introduced ExtraMapConfig to allow multiple adapter configurations.
* Updated server and handler to utilize extra maps for routing.
* Added dashboard handler for metrics visualization.

README.md

@@ -136,6 +136,11 @@ Override with `--config path/to/file.yaml` or env vars prefixed `VECNA_`.
     "truncate_mode": "from_end",
     "pad_mode": "at_end"
   },
+  "extra_maps": {
+    "512":  { "target_dim": 512 },
+    "256":  { "target_dim": 256, "type": "random", "seed": 42 },
+    "fast": { "target_dim": 768, "forward_target": "small-model" }
+  },
   "metrics": {
     "enabled": true,
     "path": "/metrics",
@@ -184,6 +189,43 @@ There is no partial migration path — a mixed index produces degraded or incorr
 
 ---
 
+## Extra maps
+
+`extra_maps` lets you expose multiple adapter configurations on a single vecna instance. Each entry is a named `AdapterConfig` whose unset fields fall back to the global `adapter` values.
+
+```json
+"adapter": { "type": "truncate", "source_dim": 1024, "target_dim": 1536 },
+"extra_maps": {
+  "512":        { "target_dim": 512 },
+  "256":        { "target_dim": 256, "type": "random", "seed": 42 },
+  "openai-alt": { "target_dim": 1536, "forward_target": "openai" }
+}
+```
+
+| Route | Forwarder | Adapter |
+|-------|-----------|---------|
+| `POST /v1/embeddings` | global default | global `adapter` |
+| `POST /map/512/v1/embeddings` | global default | `extra_maps["512"]` — target 512, rest from global |
+| `POST /map/256/v1/embeddings` | global default | `extra_maps["256"]` — random projection to 256 |
+| `POST /map/openai-alt/v1/embeddings` | `openai` target | `extra_maps["openai-alt"]` adapter |
+
+All fields are overridable per map entry:
+
+| Field | Description |
+|-------|-------------|
+| `forward_target` | Named target from `forward.targets`; empty = global default |
+| `type` | `truncate` / `random` / `projection` |
+| `source_dim` | Source dimension; falls back to global `adapter.source_dim` |
+| `target_dim` | Target dimension |
+| `truncate_mode` | `from_end` / `from_start` |
+| `pad_mode` | `at_end` / `at_start` |
+| `seed` | Seed for random projection |
+| `matrix_file` | Path to projection matrix JSON |
+
+> The same re-embedding warning applies per map — changing any setting for an `extra_maps` entry requires re-embedding all vectors indexed through that endpoint.
+
+---
+
 ## Truncation and padding modes
 
 ### `truncate_mode` — which part of the vector is kept when downscaling
@@ -242,6 +284,18 @@ POST /v1/models/{model}:embedContent
 POST /v1/models/{model}:batchEmbedContents
 ```
 
+### Extra-map routes
+
+Serve the same backing model with a different adapter per endpoint. The `{mapping}` segment matches a key in `extra_maps`.
+
+```
+POST /map/{mapping}/v1/embeddings
+POST /map/{mapping}/v1/models/{model}:embedContent
+POST /map/{mapping}/v1/models/{model}:batchEmbedContents
+```
+
+All extra-map routes require the same authentication as the standard API routes.
+
 ### OpenAPI spec and docs
 
 ```
@@ -263,7 +317,7 @@ GET /docs
 
 ## Prometheus metrics
 
-Enable in config: `metrics.enabled: true`. Scrape at `GET /metrics`.
+Enable in config: `metrics.enabled: true`. Scrape at `GET /metrics`. Human-readable dashboard at `GET /dashboard`.
 
 | Metric | Type | Description |
 |--------|------|-------------|
@@ -276,6 +330,12 @@ Enable in config: `metrics.enabled: true`. Scrape at `GET /metrics`.
 | `vecna_endpoint_errors_total` | counter | Forwarding failures by error type |
 | `vecna_tokens_total` | counter | Tokens consumed, by target, model, and type (`prompt`/`total`) |
 
+### Dashboard
+
+`GET /dashboard` renders a live HTML view of all metrics. Counters show request counts with status-code badges, histograms show p50/p95/p99 latencies, gauges show current endpoint priority and inflight counts.
+
+Auth follows the same rules as `/metrics`: server `api_keys` apply, and `metrics.api_key` adds a second layer if set.
+
 ---
 
 ## Development
@@ -315,7 +375,7 @@ Starts vecna and an Ollama instance. The `vecna_config` named volume persists th
 ### Onboard (interactive setup)
 
 ```sh
-docker compose run --rm -it vecna onboard --config /config/vecna.json
+docker compose run --rm -it vecna onboard
 ```
 
 Ollama is reachable by hostname on the Docker network — the scanner will find it automatically. After onboarding, restart the proxy:
@@ -327,17 +387,17 @@ docker compose restart vecna
 ### Query
 
 ```sh
-docker compose run --rm vecna query --compact "hello world" --config /config/vecna.json
+docker compose run --rm vecna query --compact "hello world"
 ```
 
 ### Test endpoints
 
 ```sh
 # report latency and dims
-docker compose run --rm vecna test --config /config/vecna.json
+docker compose run --rm vecna test
 
 # test and remove failing endpoints
-docker compose run --rm vecna test --config /config/vecna.json --remove-broken
+docker compose run --rm vecna test --remove-broken
 ```
 
 ### Edit config manually