feat(agent-presets): rename the two-tool preset to minimal

`core-web` said neither of the things that matter about it. The `-web`
suffix is a leftover from the whole-process `core-web.cordis.yml` overlay,
and presets are per-session and not web-specific. `core` reads as "the
foundational one" when it is in fact the one with the fewest capabilities.

`minimal` says what it is and orders the shipped set legibly by capability:
minimal, standard, cordis.

Breaking: a session created under `core-web` records that id in its header
and will fail to resolve it on resume. Nothing outside this repository has
shipped, so no migration path is offered.

The identically named `config/core-web.cordis.yml` — the legacy
whole-process overlay behind the web snapshot test — is a different thing
and keeps its name.

apps/cli/config/agent-presets/minimal/agent.cordis.yml

@@ -1,4 +1,4 @@
-# The `core-web` agent preset: the two-tool benchmark surface.
+# The `minimal` agent preset: the two-tool benchmark surface.
 #
 # The native model surface is exactly persistent `bash` plus
 # `str_replace_editor`. Everything else a session could reach — skills, goals,