refactor(engine): migrated AttributeMapper to FlowExpr

[asrcpq]

Overview

This PR continues #2030, #2087, #2109, #2122 to migrate AttributeMapper to FlowExpr.

Changes

• migrate AttributeMapper mapper fields to use FlowExpr, update schema.
• migrate workflows AttributeMapper code to FlowExpr.
• add containment check for attributes like key in attributes.
• add string join method like str.join(list).

Notes

• all direct attribute access are migrated to use valueAttribute which has same null fallback logic.
• in solar-radiation workflow, invalid AMeDAS CSV (missing column) will fail workflow instead of producing null.

[asrcpq]

Automated safety review of unsafe AttributeMapper expr migrations (check.py flagged 26 items). Each inline comment is one item to verify/resolve.

[asrcpq]

[safety review] AttributeMapperGmlPathAndFilename — attributes["path"].split("/")[-2]
Old rhai fell back to udxDirs ?? "" when len < 2. PLATEAU GML paths are always structured as .../udxDir/file.gml with ≥3 segments so [-2] always resolves. The flat 10-cons.yml counterpart already uses this same expression. Safe.

[asrcpq]

[safety review] BuildingPotentialMapper — area = attributes["totalRoofArea"] (dropped ?? 0.0)
Old rhai: let area = env.get("__value")["totalRoofArea"] ?? 0.0. Features arrive from BuildingAreaMerger:merged — only matched features reach here; unmatched go to unmerged (unwired). totalRoofArea is set by BuildingAreaAggregator (StatisticsCalculator sum, always numeric). The ?? 0.0 was defensive dead code. Safe.

[asrcpq]

[safety review] BuildingAttrExtractor (tsunamiHeight) — same pattern as floodDepth loop above. TsunamiRiskAttribute defaults to [], uro:depth defaults to 0.0. Safe.

[asrcpq]

parentTag fallback — potential error — rhai: env.get("__value").parentTag ?? env.get("__value").featureType

value: attributes.get("parentTag", attributes["featureType"])

The default expression attributes["featureType"] is always evaluated regardless. If featureType is also absent it throws, while rhai ?? would return (). Should be attributes.get("parentTag", attributes.get("featureType", "")).