fix(build): restore ai default cast-agent + Linux BUNDLE_ID

Two more release build fixes:

① crates/ai/Cargo.toml: restore default = ["cast-agent"]
  Removing the default broke Windows and native Linux builds.
  When ai is compiled without the cast-agent feature active
  (e.g. for tests) the dep:cast_agent optional dep is not
  linked, so any caller using ai::cast_agent:: fails to
  resolve the module. Restoring the default keeps cast_agent
  always linked for native targets.

  The WASM mio failure is addressed separately by running the
  release without build_web until proper wasm cfg gating lands.

② script/linux/bundle: restore missing BUNDLE_ID assignment
  The earlier fi-restoration edit accidentally omitted the
  BUNDLE_ID="dev.castcodes.$APP_NAME" line that was present
  before our edits. Without it, bundle_install and bundle_appimage
  cannot find the .desktop file for the oss channel.

Author: BunsDev

crates/ai/Cargo.toml

@@ -6,7 +6,7 @@ publish.workspace = true
 license.workspace = true
 
 [features]
-default = []
+default = ["cast-agent"]
 jemalloc = []
 local_fs = []
 test-util = []

script/linux/bundle

@@ -190,6 +190,7 @@ fi
 
 EXECUTABLE_PATH="$CARGO_TARGET_OUTPUT_DIR/$WARP_BIN"
 DEBUG_EXECUTABLE_PATH="$EXECUTABLE_PATH.debug"
+BUNDLE_ID="dev.castcodes.$APP_NAME"
 
 # Note that this variable must be set (and exported!) before we compile the
 # binary, as it is read at compile time by Linux autoupdate logic (to know the