#3437 Error and help messages still say model under swamp behavior commands (follow-up to #3431)

Follow-up to swamp-club#3431, which moved the log output and help text listed there to the behavior term. Two groups were left on purpose.

1. Strings that swamp-uat asserts, so they kept the model wording:

• extension push dry run / extension info: "Models (N):" and the push summary "Models: N" (swamp-uat tests/cli/extension/regressions/push_sub_directory_test.ts:160 matches /Models (1)/)
• data get / data rename / data delete: "Model not found: " (tests/cli/data/get_test.ts:200, rename_test.ts:52; the same message is asserted for model delete and access group add-member/remove-member)
• data delete: "No data named ... exists for model " (tests/cli/adversarial/data_delete_test.ts:185 and :281)
• model cancel: "Model not found", "Provide a model name or ID ...", "No running method runs found for model ..." (tests/cli/model/cancel_test.ts)

1. About 400 other error and help messages that still say model: invocation errors (Method X not found on model type Y), model get/edit/create/delete messages, validation warnings (Data stored under this model will vary ...), extension authoring rule texts. Most are shared by swamp model and swamp behavior commands, so a plain word swap would be wrong under swamp model.

Proposed approach: make the shared messages use the spelling the user typed (behavior under swamp behavior, model under swamp model), the way BEHAVIOR_*_SYNTAX already does for help syntax. Loosen the swamp-uat assertions above to accept either spelling first, so the change ships without breaking UAT. models/ folder names and API names such as context.runModel stay as they are.