[osipovartem]

Purpose

Preserve provenance of explicit Snowflake SQL TRY_CAST so Rustice can validate source types after parameter binding without changing internal DataFusion TryCast expressions.

Behavior

• Mark only SQL TRY_CAST planned under the Snowflake dialect; generic SQL, SAFE_CAST, and planner-inserted casts remain unmarked.
• Keep provenance non-semantic: type-only metadata propagation and same-type physical cast elision retain their fast paths.
• Remove the marker from logical and physical result fields and formatted plans, including EXPLAIN output.

Verification

• Focused unit tests cover SQL marking/display, logical output metadata, and physical same-type/metadata behavior.
• cargo +1.99.0 fmt --all -- --check and git diff --check passed on the rebased branch.
• Independent read-only review of the rebased four-file diff: approved, no blocking correctness, performance, API, or test findings.
• #166 merged the RustFS CLI test repair and inherited CI-baseline fixes into the df55 base. This branch was rebased onto that base, dropping four duplicate CI commits; only the two functional commits remain. CI on the rebased head is running.
• Full local builds remain deferred while the WSL host free-space guard is unmet. Rustice integration/routing tests are tracked in Embucket/rustice#1004.