feat(import): O(1) attention options in Advanced (cortiq >= 0.2.0)

- New Advanced controls on the import page: O(1) attention spec (off / all /
  deep N / explicit layer list) plus the --o1-m / --o1-window / --o1-sink knobs
  with validated defaults (32 / 128 / 4) and explanatory hints.
- Backend passes --o1* to the native `cortiq convert`; fails fast with clear
  messages when combined with Python-only options, used on GGUF imports, or
  when the installed cortiq predates 0.2.0 (the hint needs the new runtime).
- The hint is recorded in the .cmf header (weights byte-identical); the runtime
  applies it at load. Verified end-to-end: converted a model with --o1 all and
  the runtime logged "o1 nystrom attention: 2/2 layer(s)".

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cortiq-gateway"
-version = "0.2.14"
+version = "0.2.15"
 edition = "2021"
 rust-version = "1.75"
 license = "Apache-2.0"