Add parquet metadata subcommand and refactor parquet_tools

[thinkingfish]

Summary

• Refactors parquet_tools from a single mod.rs into a modular structure, extracting the existing annotate logic into annotate.rs
• Adds a shared read_parquet_footer() helper for reading parquet metadata and schema
• Adds a new parquet metadata subcommand for inspecting parquet files

parquet metadata subcommand

Displays file-level metadata, table geometry, and column schema for a parquet file.

Flags (filters — default shows all sections):

• --file — file-level key-value metadata only
• --geometry — logical table shape and per-row-group detail (ASCII table with human-readable byte sizes)
• --schema — column-level metadata as a pipe-delimited table with metric_type as its own column
• --json — output in JSON format for programmatic use (combinable with the above)
• --field=KEY — extract and print a single file-level metadata key (auto-pretty-prints JSON values)

Example outputs:

$ rezolus parquet metadata -i file.parquet --geometry
Geometry:
  Logical Table: 142 columns x 30000 rows

  Group | Rows  |    Bytes
  ------+-------+---------
  0     | 10000 | 4.6 MiB
  1     | 10000 | 4.6 MiB
  2     | 10000 | 4.6 MiB
  ------+-------+---------
  Total | 30000 | 13.8 MiB

$ rezolus parquet metadata -i file.parquet --schema
Schema (5 fields):
  Name             | Type    | Metric Type   | Metadata
  -----------------+---------+---------------+---------
  timestamp        | UInt64  | timestamp     | metric=timestamp
  cpu_cycles       | Float64 | delta_counter | metric=cpu/cycles
  cpu_instructions | Float64 | delta_counter | metric=cpu/instructions
  cgroup_memory    | Float64 | gauge         | metric=cgroup/memory/usage, name={...}
  request_latency  | List    | histogram     | metric=request/latency

Files changed

• src/parquet_tools/mod.rs — slimmed to command definitions, dispatch, and shared read_parquet_footer() helper
• src/parquet_tools/annotate.rs — extracted from mod.rs, unchanged behavior
• src/parquet_tools/metadata.rs — new subcommand