Add named behavior creation and verified textual authoring examples

examples/text-first/README.md

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+# Start a model in text
+
+Open `project.arcadia`, then choose **Textual model**. The model describes who
+reports distress, who assesses it, and the information passing between those
+activities. It needs no diagram or handwritten UUIDs.
+
+1. Read each declaration as **kind, alias, display name**. References such as
+   `@assess` use the alias. The two allocations state responsibility; the
+   interaction states the direction of the exchange.
+2. Change `"Assess incident"` to a name suited to your project. Use **Apply all**,
+   then **Save all**. Keep the identity clauses added to the accepted source:
+   they preserve the same model objects in later edits.
+3. Add work and exchanges as your understanding grows. Behavior coverage checks
+   identify activities and exchanges that still need process or scenario context;
+   these advisory checks allow you to save the intermediate model.
+
+Changing a display name keeps references intact. Changing an alias requires
+updating every `@alias` use. Nesting expresses decomposition; an allocation
+expresses who performs work. Neither implies the other.
+
+For a larger example with behavior, ports, views and OA/SA correspondence, use
+[the water-pressure walkthrough](../release1/README.md). The
+[language reference](../../docs/language.rst) defines all declarations and the
+rules for splitting a project into included files.

examples/text-first/project.arcadia

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+arcadia 7;
+project distress "Distress response" {
+    oa_actor vessel "Vessel in distress" {}
+    oa_entity rescue "Rescue coordination" {}
+    oa_activity report "Report distress" {}
+    oa_activity assess "Assess incident" {}
+    allocation vessel_reports "Crew reports" { source @vessel; target @report; }
+    allocation rescue_assesses "Team assesses" { source @rescue; target @assess; }
+    interaction distress_report "Distress report" { source @report; target @assess; }
+}