Add Avro and ORC parsers (data-lake siblings of Parquet)

[copyleftdev]

Implements the Avro / ORC plugins — issue #23 (the last of the 23 format issues).

Both lower to the same engine-independent Columns as the Parquet/Arrow
parsers, so no library type escapes the contract.

AvroParser (apache-avro)

Each record in the object-container file is a row; record fields become typed
columns via avro_to_value: bool/int/long/float/double/string/enum mapped;
bytes/fixed → hex Str; date/time logical types → their integer value;
unions unwrap to their held value; nested records/arrays/maps/decimals → Null
(honest absence for v1's flat-scalar lowering). Magic Obj\x01; extension .avro.

OrcParser (orc-rust → Arrow)

The file is read into Arrow record batches; each cell is rendered and run through
infer_scalar, so numbers/bools become typed columns and nulls are preserved.
Magic ORC; extension .orc. arrow is pinned to the major orc-rust uses so
the RecordBatch types unify.

Feature gating

Both behind the default-on datalake feature (binary formats); the text-only
--no-default-features build stays lean. Both builds verified.

Testing

Roundtrip tests write a tiny Avro file (apache-avro Writer) and a tiny ORC file
(orc-rust Arrow writer) in-memory — no committed binaries; avro_to_value is
unit-tested across every handled variant (incl. union unwrap, date/time, bytes);
non-format input is a clean AxError::Parse.

Gates

• fmt / clippy -D warnings / full workspace tests green (default and
  --no-default-features).
• Mutation gate: 0 surviving mutants on avro.rs. Deleting avro_to_value's
  explicit Null arm is a documented equivalent (it and the catch-all both
  return Null).

Closes #23

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 028195fb-bf62-4314-bf10-9e6b935aa87d

📥 Commits

Reviewing files that changed from the base of the PR and between d2fd02f and 5940822.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (5)

• .cargo/mutants.toml
• crates/ax-normalize/Cargo.toml
• crates/ax-normalize/src/parser.rs
• crates/ax-normalize/src/parsers/avro.rs
• crates/ax-normalize/src/parsers/mod.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/avro-orc

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