Gaps from the test projects: clear $List, CE4899 default-language captions, drop loses grants silently, missing-font note, task-outcome docs

[ako]

Gaps reported by the test projects (BankV1, ChipCoV5, CapTrackV7) and re-verified on main (54d55ff):

1. clear $List; is missing, and describe → exec breaks on it. Mendix has ChangeListActionType Clear (modelsdk/gen/microflows/enums.go:49-52). MDL parses only add … to and remove … from. describe already prints clear $X; for a Clear action that Studio Pro stored (mdl/executor/cmd_microflows_format_action.go:476), so a round trip of such a flow fails to parse. Fix: add clear $List; to the grammar and the builder (ChangeListTypeClear), and check how list Set round-trips.
2. CE4899 (empty caption in the default language) is not foreseen.
   • Repro: make de_DE the default language and drop en_US. docker check then gives "Empty caption. [German, Germany]" on Administration.Account_Overview's tabPage2.
   • Neither check -p --references nor lint reports it. QUAL005 (mdl/linter/rules/missing_translations.go:55) only compares the languages present and ignores DefaultLanguageCode.
   • Fix:
     • A rule that flags any required caption (tab page, page title, button) with no text in the default language.
     • When the default language changes, report how many texts lack it.
3. drop microflow silently loses its grants across runs. Within one script, drop + create keeps the module-role grants (rememberDroppedMicroflow, mdl/executor/executor.go:586). A drop in one run and a create in a later one loses them, which CapTrack's apply.sh hit (CE0106). drop prints only "Dropped microflow". Fix:
   • drop names the roles whose grants it removes, and says they carry over only when the create is in the same script.
   • The splice-refusal message and the skill recommend doing the drop and the create in one script.
4. theme create --from does not say a font is missing. A seeded font family that mxcli does not vendor (e.g. Inter) gets no @font-face and no file, and nothing is printed (cmd/mxcli/theme/create_seeded.go:213, planFonts). Fix: print a note naming each such family.
5. set task outcome only takes a literal, by design. Microflows$SetTaskOutcomeAction.Outcome is a by-name reference and OutcomeValue a primitive (modelsdk/gen/microflows/types.go:16249). The workflow skill and mxcli syntax should say this, so a shared "claim and complete" flow needs one branch per outcome.

[ako]

All five items are merged: 1 and 5 in #949 (clear $List;, the list Set round trip, and the set-task-outcome literal explanation); 2–4 in #948 (QUAL006 / MDL-I18N01 for CE4899, drop names lost grants, theme font note).