fix(codegen): isolate local collection scopes

[luisleo526]

Summary

• isolate callable-local array/map/matrix metadata by callable, block, and declaration identity instead of process-wide raw variable names
• activate lexical collection bindings in source order, preserving outer-RHS aliases, scalar/parameter/loop shadows, persistent members, and exact element types
• carry scoped collection context through UDF methods, tuples, drawing/header discovery, and linear request.security helper emission

Validation

• focused lexical-scope suite: 53 passed
• impacted compatibility suites: 163 passed, including frozen output hashes
• adversarial loop-binder compile matrix: 9/9
• full pinned-engine pytest: 1770 passed, 2 skipped
• Pyodide gate: 277/277 parity
• 666-source manifest: byte-identical to KI-48g baseline at 26ff05c3ba8a78fbc67c2be70fb08dc9b8a044362dd925149cbbd4b208040a7e (660 OK, same 6 errors)
• exhaustive N=3 factor matrix: 8/8, publication_gate_passed=true, fingerprint a3e2b987ca923fc25b15c75395ccb2d5c75dd9948ae96c3a528940d19c942926

Follow-up

• terminal local-array element expressions still have a pre-existing generic UDF return-type gap
• same-raw-name persistent collections across nested helper clones still share the pre-existing state-identity limitation