docs(msgs): drop stale system-ROS discovery fallback from message-generation docs

docs/bindings/python-codegen.md

@@ -293,7 +293,7 @@ flowchart TD
 accTitle: Python bindings build process from cargo build to compiled output
 accDescr: Running cargo build triggers build.rs which discovers ROS packages, parses msg files, resolves dependencies, then generates both Python type files and a Rust PyO3 module compiled into hiroz-msgs.
     A["cargo build hiroz-msgs<br/>--features python_registry"] --> B["build.rs executes"]
-    B --> C["Discover ROS packages<br/>(AMENT_PREFIX_PATH or bundled)"]
+    B --> C["Discover ROS packages<br/>(bundled assets/&lt;distro&gt; only)"]
     C --> D["Parse .msg/.srv files"]
     D --> E["Resolve dependencies<br/>(type hashes, nested types)"]
     E --> F["Generate Python files"]

docs/getting-started/building.md

@@ -149,15 +149,7 @@ cargo build --all
 
 ### Message Package Resolution
 
-The build system automatically locates ROS message definitions:
-
-**Search order:**
-
-1. System ROS installation (`AMENT_PREFIX_PATH`, `CMAKE_PREFIX_PATH`)
-2. Common ROS paths (`/opt/ros/{rolling,jazzy,kilted,lyrical,humble}`)
-3. Bundled assets (built-in message definitions in hiroz-codegen)
-
-This fallback mechanism enables builds without ROS 2 installed.
+`hiroz-msgs` generates message types entirely from the bundled asset trees in `hiroz-codegen` (`crates/hiroz-codegen/assets/<distro>/`) — it never probes a system ROS 2 installation (`AMENT_PREFIX_PATH`, `CMAKE_PREFIX_PATH`, `/opt/ros/*`). The target distro (`humble`, `jazzy`, or `lyrical`) is selected by Cargo feature; a package requested by an enabled feature but missing from that distro's asset tree is a build error, not a silent fallback. This is why `hiroz-msgs` builds without ROS 2 installed.
 
 ### Common Development Commands
 

docs/reference/troubleshooting.md

@@ -7,44 +7,30 @@
 
 ## Build Issues
 
-??? question "Build fails with 'package not found' or missing ROS 2 packages"
-    **Root Cause:** ROS 2 environment not sourced or packages not installed.
+??? question "Build fails with 'feature requested package ... but it was not found in assets/DISTRO'"
+    **Root Cause:** `hiroz-msgs` generates messages entirely from `hiroz-codegen`'s bundled asset trees (`crates/hiroz-codegen/assets/<distro>/`) — it does not read a system ROS 2 installation. An enabled package feature (e.g. `test_msgs`) has no matching package directory under the selected distro's tree.
 
     **Solutions:**
 
-    1. **Source ROS 2 environment:**
+    1. **Check which distro is selected** (`humble`, `jazzy`, or `lyrical` — defaults to `jazzy`):
        ```bash
-       source /opt/ros/jazzy/setup.bash
-       # or for rolling:
-       source /opt/ros/rolling/setup.bash
+       cargo build -p hiroz-msgs --no-default-features --features core_msgs,jazzy
        ```
 
-    2. **Verify environment variables:**
+    2. **Confirm the package exists in that distro's bundled tree:**
        ```bash
-       echo $AMENT_PREFIX_PATH
-       echo $CMAKE_PREFIX_PATH
+       ls crates/hiroz-codegen/assets/jazzy/example_interfaces
        ```
 
-    3. **Check package installation:**
-       ```bash
-       ros2 pkg prefix example_interfaces
-       # If fails, install:
-       sudo apt install ros-jazzy-example-interfaces
-       ```
+    3. **Only `humble`, `jazzy`, and `lyrical` ship a real asset tree today** — `rolling`/`kilted` features exist but have no bundled packages yet, so any package feature will fail for them.
 
-    4. **Clean and rebuild:**
+    4. **Clean and rebuild after changing feature flags:**
        ```bash
        cargo clean -p hiroz-msgs
        cargo build -p hiroz-msgs
        ```
 
-    **Common Error Messages:**
-
-    | Error | Solution |
-    |-------|----------|
-    | "Package X not found" | Source ROS 2 environment |
-    | "Cannot find ament_index" | Install ROS 2 or use bundled msgs |
-    | "AMENT_PREFIX_PATH not set" | Run `source /opt/ros/jazzy/setup.bash` |
+    If the package is genuinely missing from a distro that should carry it, that's a gap in the bundled asset tree, not a local environment problem — file an issue rather than trying to source a system ROS 2 install.
 
 ??? question "Compiler error: cannot find crate hiroz_msgs"
     **Root Cause:** `hiroz-msgs` is not part of default workspace members.

docs/user-guide/message-generation.md

@@ -61,24 +61,19 @@ hiroz-codegen's orchestration capabilities:
 
 ```mermaid
 sequenceDiagram
-accTitle: Package discovery sequence checking system then bundled message sources
-accDescr: build.rs asks the discovery layer to find packages, which checks AMENT_PREFIX_PATH then standard opt/ros paths and finally falls back to bundled assets before returning paths for Rust code generation.
+accTitle: Package discovery sequence resolving requested packages against the bundled distro asset tree
+accDescr: build.rs selects a distro from Cargo features, then asks the discovery layer to find each feature-requested package in that distro's bundled asset tree, returning paths for Rust code generation or failing the build if a requested package is missing.
     participant B as build.rs
     participant D as Discovery
-    participant S as Sources
-
-    B->>D: Find packages
-    D->>S: Check AMENT_PREFIX_PATH
-    alt Found in system
-        S-->>D: System messages
-    else Not found
-        D->>S: Check /opt/ros/*
-        alt Found in standard path
-            S-->>D: System messages
-        else Not found
-            D->>S: Check bundled assets
-            S-->>D: Bundled messages
-        end
+    participant S as Bundled assets
+
+    B->>D: Find packages (distro, requested features)
+    D->>S: Check assets/<distro>/<package>
+    alt Present
+        S-->>D: Bundled messages
+    else Missing
+        S-->>D: Not found
+        D-->>B: Build error
     end
     D-->>B: Package paths
     B->>B: Generate Rust code
@@ -180,24 +175,16 @@ let config = GeneratorConfig {
 
 ```mermaid
 flowchart LR
-accTitle: Package discovery order by feature flags and ROS installation presence
-accDescr: Feature flags trigger discovery that checks for a system ROS installation via AMENT_PREFIX_PATH or standard distro paths, falling back to bundled assets when no ROS is installed.
-    A[Feature Flags] --> B{System ROS?}
-    B -->|Found| C[AMENT_PREFIX_PATH]
-    B -->|Not Found| D{/opt/ros/distro?}
-    D -->|Found| E[Standard paths]
-    D -->|Not Found| F[Bundled assets]
-
-    C --> G[Generate from system]
-    E --> G
-    F --> H[Generate from bundled]
+accTitle: Package discovery order by distro feature and requested package features
+accDescr: A distro Cargo feature selects one bundled asset tree; each enabled package feature is then resolved against that tree, generating from bundled assets on a match or failing the build if the package is missing.
+    A[Distro feature: humble/jazzy/lyrical] --> B[assets/&lt;distro&gt;/]
+    C[Package feature: std_msgs, geometry_msgs, ...] --> D{Package in tree?}
+    B --> D
+    D -->|Found| E[Generate from bundled]
+    D -->|Missing| F[Build error]
 ```
 
-1. **System ROS:** `$AMENT_PREFIX_PATH`, `$CMAKE_PREFIX_PATH`
-2. **Standard paths:** `/opt/ros/{rolling,jazzy,kilted,lyrical,humble}`
-3. **Bundled assets:** Built-in message definitions in hiroz-codegen
-
-This fallback enables development without ROS 2 installation.
+`hiroz-msgs` generates exclusively from `hiroz-codegen`'s bundled asset trees (`crates/hiroz-codegen/assets/<distro>/`) — there is no system ROS 2 discovery (`$AMENT_PREFIX_PATH`, `$CMAKE_PREFIX_PATH`, `/opt/ros/*`). This is why builds work without a ROS 2 installation, and why a package requested by an enabled feature but absent from the selected distro's tree is a hard build error rather than a silent fallback.
 
 ## Using Generated Messages