docs(surgery): mlxcel-surgery comments still describe shipped work as future

## Summary

Update three `mlxcel-surgery` doc comments that describe shipped functionality as "future": the CLI integration, the error variants, and the five concrete ops have all landed.

## Background

The comments date from when surgery was scaffolding. Since then the CLI flag, the loader glue, the error variants, and all five ops shipped, so the "future" language now misleads a reader about what exists.

## Proposed Solution

Three comment edits, each verifiable by following the reference already in the comment.

## Implementation Notes

- `src/lib/mlxcel-surgery/src/pipeline.rs:36-37` says "Used by: future `mlxcel::surgery` integration glue (CLI flag)". The glue exists (`src/surgery.rs`) and the flag ships (`src/main.rs:329`, `Cargo.toml:113` on by default).
- `src/lib/mlxcel-surgery/src/error.rs:23-24` says "Variants cover the common failure modes for the future op set (A5-A9)". All three variants are live (`ops/add.rs`, `ops/scale.rs`, `ops/prune/tensor_ops.rs`).
- `src/lib/mlxcel-surgery/src/lib.rs:77-78` says "future concrete ops (A5-A9 - Scale, Add, Prune, Replace, Interpolate)". All five are exported at `lib.rs:60` (`pub use ops::{AddOp, InterpolateOp, PruneOp, PruneSelector, ReplaceOp, ScaleOp};`).
- Same class as the merged surgery-example cleanup (#1632 / #1643).

## Acceptance Criteria

- [ ] No `mlxcel-surgery` comment describes shipped work as future.

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## Original Suggestion

### Title: docs(surgery): mlxcel-surgery comments still describe shipped work as future

Three `mlxcel-surgery` doc comments still describe shipped functionality as "future" — the CLI integration, the error variants, and all five concrete ops have long since landed.

## Evidence

- `src/lib/mlxcel-surgery/src/pipeline.rs:36-37` — "Used by: future `mlxcel::surgery` integration glue (CLI flag — A4)"; the glue exists (`src/surgery.rs:15-21`) and the flag ships (`src/main.rs:339`, `:2623`; `src/bin/mlx_server.rs:1939`; `Cargo.toml:113` on by default)
- `src/lib/mlxcel-surgery/src/error.rs:23-24` — "Variants cover the common failure modes for the future op set (A5–A9)"; all three variants are live (`ops/add.rs:243,276,303`, `ops/scale.rs:205,225,233`, `ops/prune/tensor_ops.rs:47`)
- `src/lib/mlxcel-surgery/src/lib.rs:77-78` — "future concrete ops (A5–A9 — Scale, Add, Prune, Replace, Interpolate)"; all five are exported at `lib.rs:60`

## Suggested fix

Three comment edits, each verifiable by following the reference in the comment itself. Same class as the merged surgery-example cleanup (#1632/#1643).

## Acceptance criteria

- [ ] No `mlxcel-surgery` comment describes shipped work as future

Start with the three doc comments at src/lib/mlxcel-surgery/src/pipeline.rs:36-37, error.rs:23-24, and lib.rs:77-78. Follow the referenced integration, error variants, and exports to confirm their shipped status, then update only the misleading future wording. Done means no mlxcel-surgery comment describes shipped functionality as future.

Written by the indexing model from the issue text.