Adding migrations and lot of work. Starting work on the demo scope

migrations/026_achievements.sql

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+-- Achievements: the playthrough case-state. Boolean facts earned by a player, each
+-- remembering the story node that awarded it. This is the NARRATIVE scope the phone
+-- gate, node-enable requirements, and gates read; level-local flags (025) promote up
+-- into it when a level node's achievement fires. A fact is true once (PK on player +
+-- key); the awarding node is provenance and is nullable (New Game / manual grants).
+
+CREATE TABLE osint.achievements (
+  playthrough_id     UUID NOT NULL REFERENCES osint.playthroughs(id) ON DELETE CASCADE,
+  flag_key           TEXT NOT NULL CHECK (flag_key ~ '^[a-z][a-z0-9_.-]{0,63}$'),
+  awarded_by_node_id UUID REFERENCES osint.story_nodes(id) ON DELETE SET NULL,
+  earned_at          TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  PRIMARY KEY (playthrough_id, flag_key)
+);
+CREATE INDEX achievements_playthrough_idx ON osint.achievements (playthrough_id);
+
+COMMENT ON TABLE osint.achievements IS 'Boolean achievements earned by a player (playthrough), each remembering the awarding story node. The narrative case-state that gates the phone, node-enable requirements, and story gates.';