feat: wire data_diff tool through reladiff engine

[suryaiyer95]

Summary

• Adds data_diff TypeScript tool that wraps the Rust reladiff engine via Bridge → Python orchestrator → altimate_core.ReladiffSession
• Creates data_diff.py Python orchestrator that drives the cooperative state machine loop (start → execute SQL via ConnectionRegistry → step → repeat)
• Registers data_diff.run method in the JSON-RPC bridge dispatcher
• Adds DataDiffRunParams/DataDiffRunResult to the bridge protocol
• Updates data-diff agent prompt to use data_diff tool as primary approach (deterministic Rust engine) with manual SQL as fallback
• Depends on: AltimateAI/altimate-core-internal PR for the reladiff Rust module

Pipeline

LLM (data-diff mode) → data_diff tool (TS) → Bridge.call("data_diff.run")
→ JSON-RPC → server.py → run_data_diff() → altimate_core.ReladiffSession (Rust)
→ cooperative loop (SQL tasks ↔ ConnectionRegistry) → structured result

Test plan

• TypeScript type check passes (tsc --noEmit)
• Build succeeds (bun run build — 11 platform targets)
• End-to-end test with configured warehouse connections
• Verify data_diff tool appears in data-diff mode tool list

🤖 Generated with Claude Code

[sentry]

Bug: The _execute_task function doesn't check for error results from execute_sql, causing it to treat error messages as valid data rows and pass them to the Rust engine.
_{Severity: HIGH}

Suggested Fix

In _execute_task, check if result.columns == ["error"]. If it is, propagate the error up to the caller (run_data_diff) so it can be handled properly, instead of processing the rows. This will prevent malformed data from reaching the Rust engine and ensure failures are reported correctly.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: packages/altimate-engine/src/altimate_engine/sql/data_diff.py#L52-L63

Potential issue: The `execute_sql` function returns errors, such as connection issues or
invalid SQL, as a special `SqlExecuteResult` object with `columns=["error"]` instead of
raising an exception. The `_execute_task` function in `data_diff.py` does not check for
this error state and processes the error message as if it were a valid data row. This
leads to malformed data being passed to the Rust `ReladiffSession` engine, which can
result in incorrect diffs or opaque crashes. The `run_data_diff` function will
incorrectly report `success: True` even when a SQL execution has failed.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

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