feature: add caching-proxy clean subcommand

[maoueh]

Summary

Adds evmx caching-proxy clean <dsn> "error:<regex>" to purge wrongfully-cached error entries from the caching-proxy KV store. The parent caching-proxy command still starts the JSON-RPC server by default; clean is a new subcommand.

Motivation

Some deterministic-looking errors were cached that should not have been (now prevented going forward by the -32602 fix on develop). This command lets operators remove the already-cached bad entries by matching their error message against a regex.

Behavior

• Full-scans the store (keys are opaque sha256, so a prefix scan over all entries is required).
• Matches entries whose value is prefixed with the error marker (0x01), unmarshals the rpc.ErrResponse, and tests the regex against its Message.
• Deletes matches via BatchDelete in batches of --batch-size (default 100); --batch-size 1 deletes serially, one key per call, bypassing batching.
• --dry-run previews matches without deleting anything.
• Matcher arg is error:<regex> — the error: prefix is reserved so future matcher kinds can be added.

Report

Instead of a log line, prints a styled summary via a small local stylex package (lipgloss + go-isatty), auto-plain when stdout is not a TTY:

Caching Proxy Clean Report
──────────────────────────
  Scanned         9508
  Error entries   7736
  Matched         7727
  Deleted         0 (dry-run, nothing deleted)

Tests

• executor: TDD unit tests against a real badger store — only matching errors deleted, data + non-matching errors + malformed payloads kept; dry-run and --batch-size 1 paths; invalid batch size rejected.
• cmd/evmx: error:<regex> matcher parsing and report rendering.