FND-3856: add pyatlan_v9 creators for the 7 Sigma asset types

[cmgrote]

✨ Description

Adds creator() for the 7 Sigma asset types in pyatlan_v9: SigmaWorkbook, SigmaPage, SigmaDataElement, SigmaDataElementField, SigmaDataset, SigmaDataModel, SigmaDataModelColumn. Follows the Cognos exemplar (#1078): overlay + parity tests + integration test.

SigmaPage.creator(
    name="Summary",
    workbook_qualified_name="default/sigma/1712345678/wb1",
    workbook_name="Sales Overview",
    page_id="pg1",
)
# qualified_name == "default/sigma/1712345678/wb1/pg1"

• Exact app parity: each creator emits the qualifiedName atlan-sigma-app emits today (FND-3838 census), including the dataModels segment for data models. A different string would re-key existing Sigma assets on every tenant.
• Shape follows Table / AirflowTask: Sigma qualifiedNames are nested, so child creators take the parent's qualifiedName plus the source id. Ancestor qualifiedNames and connection_qualified_name are derived from it. Parent and ancestor names are required params, because the qualifiedName holds ids and validate(for_creation=True) requires the denormalised names.
• Parent relationship is set via Related<Parent>(unique_attributes={"qualifiedName": ...}) (sigma_workbook / sigma_page / sigma_data_element / sigma_data_model), as the app does, so creator output passes validate(for_creation=True).
• Blank inputs raise (validate_required_fields), so the app's 'unknown' placeholder collision (sigma.py:89) cannot happen. A parent qualifiedName with the wrong segment count (or, for data model columns, no dataModels segment) raises ValueError.
• asset_source_id is set on SigmaDataModel (data model id) and SigmaDataModelColumn (column id), matching the app.
• Overlays in pyatlan_v9/model/assets/_overlays/sigma_*.py; the 7 classes are regenerated from atlanhq/models with these overlays (pkl sdkOnly=python + pre-commit, the same steps as sync-python-sdk.yaml). Only the 7 Sigma classes are taken from the regeneration; other drift from models master is left to the sync workflow.

Linear: FND-3856 (analysis table in the issue comments)
Paired models PR: https://github.com/atlanhq/models/pull/2082 — adds the matching qualifiedNameFormula, which drives the regenerated _QUALIFIED_NAME_PATTERN. Merge order: this PR first, then models#2082. The sync bot regenerates from atlan-python main's overlays when models master changes, so merged in this order its PR is a no-op for the Sigma classes; the other way round it would regenerate them without the creators.

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🧩 Type of change

• 🚀 New feature (non-breaking change that adds functionality)

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✅ How has this been tested?

• tests_v9/unit/model/sigma_*_test.py, one file per type (118 tests): literal app qualifiedName, validate(for_creation=True) (including the pattern), parent unique_attributes and denormalised attrs, None / blank for every param, malformed parent qualifiedNames, create alias, updater (+ missing inputs), trim_to_required.
• App vs creator: 1,792 records run through atlan-sigma-app's own SigmaTransformer (all 7 types, ids with - _ . ~) give qualifiedNames, serialised parent refs ({typeName, uniqueAttributes}), denormalised parent qns / names and assetSourceId identical to the creators; 0 mismatches (app at 550376c).
• Mutation check: changing the dataModels segment fails the parity tests.
• Generator fidelity: models master + main's overlays reproduces main's 7 Sigma classes byte-for-byte; models#2082 + these overlays reproduces this PR's classes byte-for-byte.
• tests_v9/integration/sigma_asset_test.py: creates a Sigma connection and every Sigma type through its creator, retrieves each and asserts the exact qualifiedName, connector, parent link and denormalised attrs, then purges. Collected locally; runs in CI.
• pytest tests_v9/unit: 8028 passed, 5 skipped. pre-commit clean on all changed files.

CI (run 39278697037, with the run_pyatlan_v9_integration_tests label)

• Green for this PR's files: v9-integration-tests (tests_v9/integration/sigma_asset_test.py) and v9-qa-checks-and-unit-tests on 3.9–3.14.
• Pre-existing, not from this PR: 44 other integration jobs fail (sync v9, async v9 aio/* and legacy tests/integration), plus some cancelled jobs. Each of the 44 also fails or is cancelled on the same day's runs for FND-3857 (39278661620) or FND-3846 (39277871485). This PR touches only the Sigma files in pyatlan_v9 and tests_v9.

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📋 Checklist

• My code follows the project’s style guidelines
• I’ve performed a self-review of my code
• There are no new warnings from my changes
• I’ve added tests to cover my changes
• All new and existing tests pass locally

🤖 Generated with Claude Code

https://claude.ai/code/session_0166vmu2bYFX2P4LFGH3GR4F

[linear]

FND-3856