feat(storage): native column types + dev-branch auto-materialize (0.25.0)

[padak]

Closes #192. Closes #222.

Summary

kbagent storage create-table now accepts native backend column types with length, plus per-column --not-null / --default flags. In a dev branch the target bucket auto-materializes on the first write (mirrors the official Keboola Go CLI's EnsureBucketExists). Bumps the CLI to v0.25.0.

kbagent storage create-table --project p --bucket-id in.c-sales --name orders \
  --column 'pk:VARCHAR(40)' \
  --column 'amount:NUMERIC(18,2)' \
  --column 'ts:TIMESTAMP_TZ' \
  --column 'meta:VARIANT' \
  --column 'is_paid:BOOLEAN' \
  --primary-key pk \
  --not-null pk --not-null amount \
  --default amount=0 --default is_paid=false

The Storage API derives basetype automatically and validates type/length per backend; the CLI does only syntactic validation (regex). Removing the hard-coded VALID_COLUMN_TYPES whitelist means BigQuery/Redshift/Synapse native types pass through without per-backend code changes.

What's in the box

Layer	Change
Service (storage_service.py)	New helpers _parse_column_spec, _parse_default_assignments, _ensure_bucket_exists_in_branch. create_table gains not_null_columns + defaults kwargs and surfaces auto_created_bucket: bool in the response. column_details (in get_table_detail) now also returns native_type, length, default from KBC.datatype.* metadata -- backwards-compatible.
CLI (commands/storage.py)	New --not-null COL (repeatable) and --default NAME=VALUE (repeatable). Updated --help with two-tier examples (basic + native types). Human-mode output prints a yellow note when auto_created_bucket=true.
Hints (hints/definitions/storage.py)	Service mode passes the new kwargs; client mode notes the column-dict shape conversion.
Context (commands/context.py)	Updated signature + native-types examples + branch materialize behaviour.
Constants (constants.py)	Removed VALID_COLUMN_TYPES (whitelist no longer maintained -- API validates).
Tests	13 new service-level tests in tests/test_storage_write.py. New E2E class TestE2EStorageNativeTypesAndBranchMaterialize round-trips VARCHAR(40)/NUMERIC(18,2)/TIMESTAMP_TZ/VARIANT/BOOLEAN to Snowflake (27s wall clock).
Skill / agent	New references/storage-types-workflow.md, updated gotchas.md, updated keboola-expert.md (tool matrix + inline gotchas), regenerated SKILL.md decision table.
Docs	New TUTORIAL §8 with Snowflake type cheat sheet + retype-after-profiling example. New VHS demo docs/demos/demo-storage-types.tape -> 408 KB rendered GIF. README + CLAUDE.md command surface updated.
Versioning	pyproject.toml, plugin.json, marketplace.json synced via make version-sync. New changelog entry.

Test plan

• make check passes (ruff lint + format-check + skill-check + changelog-check + 2311 unit tests + error-codes scan)
• make skill-gen shows no diff after commit
• E2E test TestE2EStorageNativeTypesAndBranchMaterialize passes against the live padak-2-0 Snowflake project (27.88s)
• Manual round-trip on padak-2-0: create-bucket -> create-table with VARCHAR(40)/NUMERIC(18,2)/TIMESTAMP_TZ/VARIANT/BOOLEAN -> table-detail (column_details shows native_type + length + nullable + default) -> delete-bucket cascade
• Dev-branch auto-materialize verified end-to-end on padak-2-0 (response carries auto_created_bucket: true on first write, false on subsequent writes to the same bucket)
• kbagent storage create-table --help displays the new flags and examples
• kbagent --hint client and kbagent --hint service both produce valid Python for the new flags
• kbagent context documents the native-type syntax + branch materialize behaviour

Demo

Backwards compatibility

• All existing --column name:TYPE forms keep working (STRING/INTEGER/NUMERIC/FLOAT/BOOLEAN/DATE/TIMESTAMP).
• Service signature gains two new kwargs with None defaults -- existing callers unaffected.
• column_details adds three new optional keys; old keys (type, nullable, description) unchanged.
• One CLI test (test_create_table_invalid_column_type) was rewritten as test_create_table_malformed_column_spec because the whitelist is gone -- unknown type strings now flow to the API instead of being CLI-rejected.