Semantic layer: build_model push-loop transactional rollback

[ottomansky]

Background

SemanticLayerService.build_model (services/semantic_layer_service.py) generates a heuristic model from a list of storage tables and pushes it to the metastore in dependency order via _push_built_model (_semantic_layer_internals.py):

POST semantic-model -> get model UUID
for each plural in PUSH_ORDER:
    for each item in generated[plural]:
        POST semantic-X (with modelUUID = model UUID)

There is no rollback if a child POST fails after the model has been created. The model + already-POSTed children remain in the metastore.

Problem

If build_model fails halfway through (e.g. constraint regex rejected by the server, network drop mid-push), the operator is left with a partially-populated model that:

• Cannot be cleanly retried (duplicate-name POSTs return ALREADY_EXISTS).
• Cannot be kbagent semantic-layer model delete-d in one shot (refuses while children exist).
• Has to be torn down by hand: kbagent semantic-layer remove ... per child, then model delete.

Acceptance criteria

• Either: implement a rollback path that on failure tracks every successfully-POSTed item (model + children) and DELETEs them in reverse order, restoring the project to its pre-build state.
• Or: document the current non-transactional behavior in gotchas.md with the manual teardown recipe, and surface a --keep-on-failure flag (mirrors kbagent data-app create --keep-on-failure) so CI scripts can opt into preserve-state-on-failure for debugging.
• Update the build_model docstring + keboola-expert.md to reflect the chosen semantics.

Filed from PR #293 review (pre-merge follow-up tracking)

[padak]

Fixed in v0.41.10 via #303.

semantic-layer build now rolls back successfully POSTed children in reverse PUSH_ORDER when a child POST fails mid-push, and deletes the model itself if kbagent created it during this call. The wrapped KeboolaApiError carries a details.rollback envelope with full diagnostics (attempted, posted_children, deleted, failed_deletes, model_created_here, model_deleted, model_delete_error, model_uuid).

A new --keep-on-failure flag mirrors data-app create --keep-on-failure and preserves the partial state for forensic inspection — useful in CI to debug why a build broke without losing the evidence.

Release notes: https://github.com/padak/keboola_agent_cli/releases/tag/v0.41.10