docs(targets): document built-in and env droid aliases

- add README guidance for ccsd argv[0] auto-target behavior

- document CCS_DROID_ALIASES runtime extension in architecture docs

docs/system-architecture/target-adapters.md

@@ -355,6 +355,7 @@ ccs --target droid glm
 
 ```bash
 # Create alias/symlink to auto-select droid target
+# Built-in alias: ccsd
 ln -s /path/to/ccs /path/to/ccsd
 
 # Usage
@@ -365,6 +366,8 @@ ccsd glm
 
 On Windows, `ccsd.cmd`, `ccsd.bat`, `ccsd.ps1`, and `ccsd.exe` wrappers are also recognized.
 
+Additional alias names can be configured at runtime via `CCS_DROID_ALIASES` (comma-separated). Example: `CCS_DROID_ALIASES=ccs-droid,mydroid`.
+
 ---
 
 ## Registry and Lookup