fix(dynamodb): PartiQL UPDATE param order, nested REMOVE, non-ASCII WHERE panic

[vieiralucas]

Bug-hunt batch 2 (cycle 6). Three DynamoDB fixes.

• PartiQL UPDATE positional params swapped (HIGH, data corruption). UPDATE t SET x=? WHERE y=? bound the SET value from the WHERE parameter and vice versa — WHERE was evaluated from parameter index 0 and SET started after it. Since SET is textually first, SET now consumes parameters[0..set_count] and WHERE the rest.
• UpdateExpression nested REMOVE no-op (HIGH). REMOVE profile.middle / REMOVE tags[0] removed a literal top-level key named "profile.middle" instead of descending. A new remove_path resolves dotted map paths and list indices (mirroring the SET writer); missing paths stay a silent no-op like AWS.
• Non-ASCII WHERE panic (HIGH, DoS). split_partiql_and_clauses uppercased with Unicode to_uppercase() (can change byte length) then sliced by byte indices bounds-checked against the original string — a length-shrinking char ('ff' -> "FF") ran the slice past the end and dropped the connection. Now to_ascii_uppercase(), keeping buffers byte-aligned.

Tests

Unit: remove_path (nested map / list index / missing-path no-op), non-ASCII split no-panic. E2E: parameterized UPDATE order round-trip, nested REMOVE round-trip. Full dynamodb lib suite (322) + partiql e2e (7) green.

Builds clean; clippy --all-targets -D warnings clean; fmt clean.

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Summary by cubic

Fixes three DynamoDB issues: corrects PartiQL UPDATE parameter binding order, makes REMOVE handle nested paths and list indices, and prevents a panic on non-ASCII WHERE clauses. Prevents wrong-row matches/writes and avoids connection drops on Unicode input.

• Bug Fixes
  • PartiQL UPDATE: bind ? in textual order. SET consumes the first N params; WHERE uses the rest.
  • UpdateExpression REMOVE: resolves dotted paths and list indices (e.g., profile.middle, tags[0]). Missing paths are no-ops.
  • WHERE parser: use ASCII uppercasing to keep byte alignment and avoid slicing panics on chars like ff.

^{Written for commit 60d431d. Summary will update on new commits.}