feat(functions): expose retry policies in Python and Rust (#4873)

Expose `FunctionRetryPolicy` on Function declarations and refresh
overrides, together with `error_policy` and recorded attempt counts.
Python uses the Rust validation rules before sending a request; local
refreshes reject these Enterprise options.

The policy bounds calls and backoff, supports
class/message/provider-code matching, and can disable retries with
`max_attempts=1`. Batch retry and skip operate on the whole failed call.
Requires Enterprise server support for the new policy.

Validation: rebuilt the Python extension; 47 targeted Python tests and
10 Rust tests passed. Python `make check`, Rust formatting, and `cargo
clippy --features remote --tests --examples -- -D warnings` passed. The
additional repository-root Ruff sweep reports existing errors under
`docs/web-tests`; the Python workspace checks pass.

Draft user guidance covers the supporting server requirement, safe
repetition of partial work and whole-batch exhaustion. The guide
sections stay hidden until release. Vale 3.24.0 passed for the added
draft prose; no paired deployed SDK/server retry acceptance was run.
Companion server: https://github.com/lancedb/sophon/pull/9812.

BREAKING CHANGE: Rust callers constructing `FunctionRegistrationRequest`
or `FunctionErrorRecord` with struct literals must supply the new
`retry_policy` or `attempts` field, respectively.

docs/src/python/python.md

@@ -465,6 +465,8 @@ with BlobReader(read_range, len(payload)) as reader:
 
 ::: lancedb.functions.FunctionRegistrationRequest
 
+::: lancedb.functions.FunctionRetryPolicy
+
 ::: lancedb.functions.FunctionArtifactRequest
 
 ::: lancedb.functions.FunctionArtifactContent