feat(mcp/connect): catch slug-length 50-char trap before Connect 500s

[jjackson]

Summary

Closes the LearnModule.slug / DeliverUnit.slug 50-char trap that 500'd Phase 4 of leep-paint-collection/20260517-1515 opaquely. Connect's slug columns are SlugField() with the Django default max_length=50; Nova's compile_app derives slugs as module_<index>_<slugified-name>; module names ≥ ~40 chars overflow. Postgres DataError: value too long for type character varying(50) raised inside sync_learn_modules_and_deliver_units falls through program/api/views.py:102's narrow except and surfaces as HTTP 500 with empty body from connect_create_opportunity.

Same shape as the 2026-05-12 short_description 50-char trap, different boundary (slug is server-extracted from CCZ XML, not sent through any serializer). The 2026-05-12 generalized serializer-vs-model length probe (still pending) would NOT have caught this.

Four-layer fix (defense-in-depth)

• mcp/connect/backends/commcare.ts — simulateConnectSync projection now exposes slug_length_limit: 50, max_slug_length, and per-type oversized_slugs[]. New exported SLUG_LENGTH_LIMIT constant for lock-step bumping when the upstream column widens.
• skills/app-release/SKILL.md § Step 6 — release-time gate extended from collision_count === 0 && per-type > 0 to ALSO require every oversized_slugs.* empty. [BLOCKER] brief lists each offender as <type>: <slug> (<length> chars, in <first_seen_in>). Structural backstop — catches even operator-driven manual Nova edits.
• skills/pdd-to-learn-app/SKILL.md + skills/pdd-to-deliver-app/SKILL.md — new REQUIRED clause in the architect brief template: module / deliver-unit names must be ≤ 40 chars (Nova prefix + slugify + Connect column limit). Includes removal criterion tied to the upstream commcare-connect fix.
• docs/learnings/2026-05-17-connect-slug-length-50-char-trap.md + registry update — documents the bug, the prior-framing refutations (CCZ-marker over-strip and time_estimate: NULL were both wrong before Sentry pinned it), the Sentry proof, and the upstream Connect fix needed (SlugField(max_length=255) + migration). docs/learnings/2026-05-12-boundary-probe-registry.md updated with the new shipped probe + annotation on the still-pending generalized probe explaining why it'd miss this class.

Tests

5 new vitest cases in test/mcp/connect/unit/connect-sync-projection.test.ts (boundary projection — every projection exposes the new fields; learn_module + deliver_unit slugs > 50 flagged; empty projection sensible defaults; 50-char slugs do NOT trigger). All 13 tests pass.

Reproducer

leep-paint-collection run 20260517-1515 Phase 4. Module 6 name "Stage 2: Sample Preparation, Drying, Bagging, Shipment" produces slug module_6_stage_2_sample_prep_drying_bagging_shipment (52 chars). Pre-fix: opaque HTTP 500. Post-fix: app-release Step 6 halts with a [BLOCKER] naming the offender + remediation; the architect brief constraint also prevents the long name being emitted in the first place.

Recovery for the affected run

Rename Nova module 6 to a shorter active title (e.g. "Stage 2: Sample Prep + Shipment" → slug module_6_stage_2_sample_prep_shipment = 38 chars), re-build + re-release Learn, resume /ace:run leep-paint-collection/20260517-1515.

Upstream follow-up

Separate Connect PR will bump LearnModule.slug + DeliverUnit.slug to SlugField(max_length=255) + migration. Also worth proposing: extend program/api/views.py:102's except clause to catch DataError / IntegrityError and return HTTP 400 with the offending column name — converts every future column-width trap (any field, any path) from "opaque 500" to "actionable 400."

Test plan

• npx vitest run test/mcp/connect/unit/connect-sync-projection.test.ts — 13 pass
• After merge + /ace:update, re-run /ace:run leep-paint-collection/20260517-1515 with a shortened M6 name and confirm Phase 4 proceeds.
• After merge: a future Nova build with an over-length module name now halts at app-release Step 6 with the new [BLOCKER] brief instead of leaking to Connect.

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