add content-addressed hak source mode (#7)

Reviewed-on: #7
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

docs/command-surface.md

@@ -45,6 +45,22 @@ crucible changelog [args]   -> legacy `build-changelog`
 `crucible list` is machine-readable so CI can enumerate builders without parsing
 help text.
 
+## HAK builder source modes
+
+```text
+build-haks [--hak <hak-name> ...] [--archive <archive-name> ...]
+  [--source-manifest <path>] [--content-addressed-root <path>]
+  [--plan-only] [--skip-music] [--music-dataset <id> ...]
+  [--quiet|--verbose|--debug]
+```
+
+When a source manifest contains `asset_sources`, pass
+`--content-addressed-root <directory>` (or
+`--content-addressed-root=<directory>`). Crucible resolves each declared SHA-256
+under `sha256/<first-two>/<next-two>/<full-sha256>` and verifies streamed bytes
+while writing the selected HAK archives. Source manifests without
+`asset_sources` continue to use the configured assets tree.
+
 ## Global flags (planned, at wiring time)
 
 `--quiet`, `--verbose`, `--debug` (the legacy verbosity model), passed after the