feat: support more OPs

[kerthcet]

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Special notes for your reviewer

Does this PR introduce a user-facing change?

Summary by CodeRabbit

• New Features
  • Added array operations for normalization, sorting, reshaping, slicing, selection, and combining arrays, along with support for additional data types.
  • Added fast neural-network operations, including layer and RMS normalization, rotary embeddings, and scaled dot-product attention with masking.
  • Added loading and saving of Safetensors files.
• Documentation
  • Expanded the architecture overview and added instructions for running a transformer attention example.

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[kerthcet]

/kind feature

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[kerthcet]

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📝 Walkthrough

Walkthrough

mlxcore adds array operations, fused fast-kernel wrappers, and SafeTensors file I/O. A new attention example uses QKV projection, rotary embeddings, masked scaled dot-product attention, output projection, and layer normalization.

Changes

mlxcore API expansion

Layer / File(s)	Summary
Array operations and vector support crates/mlxcore/src/lib.rs, crates/mlxcore/src/vector.rs, crates/mlxcore/src/array.rs, README.md	Array gains dtype conversion, math, sorting, shape, indexing, and combining operations. VectorArray supports multi-array operations. The README lists the wrapped module functionality.
Fused kernels and attention example crates/mlxcore/src/fast.rs, crates/mlxcore/examples/attention.rs, README.md	The fast module adds normalization, RoPE, and scaled dot-product attention wrappers. The example composes these operations into a transformer attention block with a sliding-window mask.
SafeTensors file operations crates/mlxcore/src/io.rs	The io module adds functions to load named arrays from and save named arrays to SafeTensors files, with tests for round trips and error cases.

Priority: ⚪ Not assessed

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant AttentionExample
  participant Array
  participant FastKernels
  AttentionExample->>Array: Project and reshape QKV
  AttentionExample->>FastKernels: Apply RoPE to queries and keys
  AttentionExample->>FastKernels: Run masked scaled dot-product attention
  AttentionExample->>Array: Merge heads and project output
  AttentionExample->>FastKernels: Apply layer normalization

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Merge Risk: 🔵 Low · up to 174d9

This PR adds many array operations, fused kernels, and SafeTensors I/O. The only issue found is a misleading error message when an out-of-range negative axis is passed to slice_axis. It is safe to merge with that small follow-up.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately identifies the pull request as a feature that adds support for more operations. It is broad and does not identify the main areas, such as array operations, fast kernels, and safet…
Docstring Coverage	✅ Passed	Docstring coverage is 86.54% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 104 functions across 6 files. (1 skipped: 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
In `@crates/mlxcore/src/array.rs`:
- Around line 951-955: Update the axis validation in slice_axis to retain the
caller’s original axis before normalization and use that requested value in the
out-of-range error message; continue using the normalized axis for validation
and slicing.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

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Run ID: e357da4a-65ca-4790-b58b-02357b8f9531

📥 Commits

Reviewing files that changed from the base of the PR and between 6a7e68e and 174d934.

📒 Files selected for processing (7)

• README.md
• crates/mlxcore/examples/attention.rs
• crates/mlxcore/src/array.rs
• crates/mlxcore/src/fast.rs
• crates/mlxcore/src/io.rs
• crates/mlxcore/src/lib.rs
• crates/mlxcore/src/vector.rs

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[kerthcet]

/lgtm
/approve

[InftyAI-Agent]

Approved: PR has both lgtm and approved labels