build(mise): the packager tools are pinned when the trial recipe exists

P11a step 0 pinned cargo-packager, cargo-packager-updater and
cargo-generate-rpm for the trial it did not run. mise-action compiles
every pinned tool on every CI run of every job, so three cargo tools
nobody calls yet would cost minutes per run. They return to mise.toml
with the recipe that calls them (AGENTS.md: if a recipe needs a tool,
it goes in mise.toml), when the trial step starts.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

mise.toml

@@ -23,8 +23,3 @@ node = "26"
 # A compile cache shared by every jj workspace's target dir: point
 # cargo's build.rustc-wrapper at it (~/.cargo/config.toml).
 sccache = "0.18.0"
-
-# P11a: the packaging trial and the installers (docs/packaging.md).
-"cargo:cargo-packager" = "0.11.8"
-"cargo:cargo-packager-updater" = "0.2.3"
-"cargo:cargo-generate-rpm" = "0.21.1"