lcameraDev: add resolve-only deviceSelector API and deduplicate resolve paths.

Export lcameraDev_resolveDeviceSelectorCReq for attach-identity consumers,
factor live-camera snapshot helpers, and share resolveDeviceSelectorAgainstRecords
with get-or-create session acquisition.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/lcamera-dev-lib.md

@@ -117,15 +117,33 @@ Possible future params (not implemented in v1):
 
 ### `lcameraBuff()` stim-buff-api params
 
-Reserved for per-producer options (frame rate caps, pixel format preference).
-Channel selection is driven by the qualeIface name, not by stim-buff-api params.
+Channel selection is driven by the qualeIface name (`colour-yuv-y/u/v`), not by
+stim-buff-api params. Params configure the shared camera mode for all three
+attachments on the same device.
 
-Possible future params:
+**Resolution (mutually exclusive — use one group only):**
 
-* `fps-hz=30`
-* `width=640|height=480`
-* `pixfmt=NV12` — negotiation hint for `lcameraBuff` stream setup (not
-  `lcameraDev`)
+| Group | Synonyms | Meaning |
+|---|---|---|
+| Explicit dimensions | `frame-width`, `frame-w`, `dimension-width`, `dimension-w`, `dim-width`, `dim-w` | Capture width in pixels |
+| Explicit dimensions | `frame-height`, `frame-h`, `dimension-height`, `dimension-h`, `dim-height`, `dim-h` | Capture height in pixels |
+| Vertical shorthand | `vertical-resolution`, `v-resolution`, `v-res`, `vres` | Preset token: `360`, `360p`, `480`, `480p`, `720`, `720p`, `1080`, `1080p` |
+
+**Other params:**
+
+| Synonyms | Meaning |
+|---|---|
+| `colorspace`, `color-space`, `colourspace`, `colour-space` | Semantic colour model (`yuv` in v1) |
+| `full-planar-is-optional`, `opt-planar` | Allow semi-planar or packed YUV when fully planar is unavailable (presence or empty value means enabled; use `=false` to disable) |
+
+Example:
+
+```text
+lcameraBuff(v-res=480p|colour-space=yuv|opt-planar)
+```
+
+Stage 2 (`lcameraBuff`) attach/configure/classify is implemented; capture daemon
+and frame publication remain future work.
 
 ## Device selector format
 
@@ -256,13 +274,13 @@ Rules:
   (conflicting mode requests on the same physical camera).
 * `fullPlanarIsOptional == false` (default): must select a fully planar YUV
   format or throw with candidate-format diagnostics.
-* `fullPlanarIsOptional == true`: rejected at the configure API until
-  `lcameraBuff` implements non-planar producer deinterleaving (Stage 2). The
-  policy helper still accepts optional planar selection for future use.
+* `fullPlanarIsOptional == true`: may select semi-planar or packed YUV (e.g.
+  `YUYV` on UVC webcams). `lcameraBuff` classifies the layout and sizes channel
+  placeholder buffers; OpenCL deinterleave and capture start are later stages.
 
 Streaming, frame delivery, and per-frame colourspace work remain **out of scope**
-for `lcameraDev`; `lcameraBuff` uses the configured session to allocate buffers
-and start capture on attach.
+for `lcameraDev`; `lcameraBuff` uses the configured session for attach-time
+setup and will allocate capture buffers / start streaming in later stages.
 
 ## dlopen API
 
@@ -298,6 +316,9 @@ struct LcameraDevGetOrCreateResult
 typedef sscl::co::ViralNonPostingInvoker<LcameraDevGetOrCreateResult>
     lcameraDev_getOrCreateDeviceCReqFn(const std::string& deviceSelector);
 
+typedef sscl::co::ViralNonPostingInvoker<CameraIdentityRecord>
+    lcameraDev_resolveDeviceSelectorCReqFn(const std::string& deviceSelector);
+
 typedef sscl::co::ViralNonPostingInvoker<void>
     lcameraDev_releaseDeviceCReqFn(
         const std::shared_ptr<CameraSession>& deviceSession);
@@ -308,6 +329,24 @@ Failures throw `std::exception`. `lcameraBuff` holds the returned
 session wraps the acquired `libcamera::Camera`; higher layers configure the mode
 then stream from that handle.
 
+### Selector resolution (resolve-only)
+
+```cpp
+typedef sscl::co::ViralNonPostingInvoker<CameraIdentityRecord>
+    lcameraDev_resolveDeviceSelectorCReqFn(const std::string& deviceSelector);
+```
+
+Parses and resolves a `deviceSelector` against the live libcamera camera list
+using the same narrowing rules as `getOrCreateDeviceCReq`, but does **not**
+create a session, acquire a camera, or change session refcounts. Use this when
+a consumer already holds session-scoped state keyed by `CameraIdentityRecord::id`
+(for example `lcameraBuff` detach) and only needs the canonical resolved camera
+identity from an input DAP line.
+
+Internally both resolve-only and get-or-create paths share
+`resolveDeviceSelectorAgainstRecords()` in `selectorResolve.cpp` and the live
+camera snapshot helpers in `cameraManagerState.cpp`.
+
 ### Session mode configuration
 
 ```cpp