vendor/clawdforge: refresh SDK — adds SystemMode::Replace for personas

Re-vendored from clawdforge@d4c3a9d. RunRequest now carries
`system_mode: Option<SystemMode>` where SystemMode is Append (the
default, current behavior — append to claude's base prompt) or
Replace (new — replaces claude's base prompt entirely).

Replace mode is the unlock for v0.3 author personas: Orson Black /
Sulkta as authors can't have Claude's default helpful-honest
defaults bleeding through. Replace makes the model BECOME the
persona instead of 'Claude playing the persona.'

Existing skald::summarize call stays on default (Append) — the
summarizer is more 'tool-use over text' than persona, and Claude's
defaults help there. The gen + cleanup passes will switch to
Replace once authors are wired (next step).

vendor/clawdforge/src/lib.rs

@@ -54,5 +54,5 @@ pub use error::Error;
 pub use session::{Session, SessionList, SessionOptions, SessionState, TurnEvent, TurnResult};
 pub use types::{
     AppToken, AppTokenInfo, FileToken, Healthz, RunFailure, RunRequest, RunResult,
-    TokenCreateRequest, TokenList,
+    SystemMode, TokenCreateRequest, TokenList,
 };