feat(programs): first-class program model — init_/compile_/root_ ladder, seeded root-kubernetes-foundations

- migrations/019: programs table (slug PK, matching assessment_definitions/cohorts
  convention), family (init/compile/root) and delivery_mode (self_paced/cohort/hybrid) as real
  CHECK-constrained enums, versioned like assessment_definitions so an edit to
  curriculum_path/delivery_mode never silently changes what an existing enrollment means. Seeds
  exactly one program wrapping the existing RootNode/Kubernetes curriculum and capstone — no
  new curriculum content invented.
- programs.js: list/get/create/update, with automatic version bump only when a
  snapshot-relevant field actually changes.

platform/api/migrations/019_programs.sql

@@ -0,0 +1,45 @@
+-- Phase 5B §2 — programs: first-class learning products, distinct from curriculum JSON itself
+-- (a program is the commercial/academic unit a student enrolls in; curriculum_path is still
+-- just the content it points at, unchanged since Phase 1). program_id IS the slug — same
+-- convention as assessment_definitions/cohorts (a single TEXT primary key, no separate numeric
+-- id + slug pair).
+--
+-- family is the init_/compile_/root_ youth-engineering ladder (see
+-- docs/PHASE5B_SELF_PACED_ENROLLMENT.md §1) — only 'root' has real curriculum content today;
+-- init/compile rows can be added later without a schema change, they just won't have a working
+-- curriculum_path yet. delivery_mode describes how the program is normally taken; an
+-- individual enrollment can still snapshot a different mode (see 020_enrollments.sql).
+--
+-- version is a plain incrementing integer, matching assessment_definitions' existing
+-- versioning convention — enrollments snapshot the version+curriculum_path they were created
+-- against so a later edit to a program never silently changes what an already-enrolled
+-- student is being held to.
+CREATE TABLE IF NOT EXISTS programs (
+  program_id               TEXT PRIMARY KEY,        -- slug, e.g. 'root-kubernetes-foundations'
+  name                      TEXT NOT NULL,
+  description               TEXT,
+  family                    TEXT NOT NULL CHECK (family IN ('init', 'compile', 'root')),
+  delivery_mode             TEXT NOT NULL DEFAULT 'self_paced' CHECK (delivery_mode IN ('self_paced', 'cohort', 'hybrid')),
+  curriculum_path           TEXT NOT NULL DEFAULT 'rootnode-path',
+  completion_assessment_id  TEXT REFERENCES assessment_definitions(assessment_definition_id),
+  estimated_duration_hours  INTEGER,
+  version                   INTEGER NOT NULL DEFAULT 1,
+  status                    TEXT NOT NULL DEFAULT 'active' CHECK (status IN ('active', 'inactive')),
+  created_by                UUID REFERENCES instructors(instructor_id),
+  created_at                TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at                TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_programs_status ON programs(status);
+CREATE INDEX IF NOT EXISTS idx_programs_family ON programs(family);
+
+-- Seed: the one legitimate self-paced program this phase ships, wrapping the EXISTING
+-- RootNode/Kubernetes curriculum and capstone — no new curriculum content invented. init_/
+-- compile_ programs are intentionally NOT seeded (no real curriculum for them yet, per this
+-- phase's explicit scope line).
+INSERT INTO programs (program_id, name, description, family, delivery_mode, curriculum_path, completion_assessment_id, estimated_duration_hours)
+VALUES (
+  'root-kubernetes-foundations', 'ROOT — Kubernetes Foundations',
+  'Self-paced Linux, containers, and Kubernetes operations — the existing RootNode curriculum, from Foundations through the RootNode Capstone.',
+  'root', 'self_paced', 'rootnode-path', 'rootnode-capstone', 40
+) ON CONFLICT (program_id) DO NOTHING;