Add rust-analyzer inlay hints tool

[qkal]

Summary

• Add readonly ra_inlay_hints MCP tool with whole-file or selected-range requests, kind filtering, bounded grouped output, and optional raw hints.
• Add rust-analyzer textDocument/inlayHint client support plus formatter/validation helpers.
• Update README/tool instructions and integration coverage while preserving the existing rename-preview and cargo-build tools from main.

Testing

• cargo fmt --check
• cargo test --locked --all
• cargo clippy --locked --all-targets -- -D warnings

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Summary by CodeRabbit

• New Features

  • Added inlay hints tool to query and preview Rust-analyzer inlay hints with support for line-range filtering, kind-based selection, and configurable result limits.

• Documentation

  • Updated README to document inlay hints functionality and clarify that Rust-analyzer query tools are read-only analysis tools.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: a748ac04-6d7b-41e4-8b3c-f780305fad63

📥 Commits

Reviewing files that changed from the base of the PR and between eebca40 and 1527ca6.

📒 Files selected for processing (1)

• src/ra/inlay_hints.rs

📝 Walkthrough

Walkthrough

This PR adds a complete ra_inlay_hints MCP tool that requests, validates, filters, groups, and formats rust-analyzer inlay hints with support for line ranges, kind filtering, truncation, and optional raw output. Changes span request parameter contracts, validation and formatting logic, LSP client support, server orchestration, documentation, and integration tests.

Changes

Inlay Hints Feature Implementation

Layer / File(s)	Summary
Request Parameters & Limits src/ra/params.rs	InlayHintsParams struct defines file path, optional line range, kind filters, max-hints override, and raw-hints flag; DEFAULT_MAX_INLAY_HINTS (200) and MAX_INLAY_HINTS (1000) constants establish configuration bounds; schema and constant tests included.
Validation, Filtering & Formatting Logic src/ra/inlay_hints.rs	Core module provides max_hints_value, request_range, parse_kind_filters, read_source_lines, and format_inlay_hints helpers that validate parameters, map inclusive line ranges to LSP Range, filter by kind, sort by position, truncate with tracking, group by line with source text, render labels, and optionally include raw hints; comprehensive unit tests cover range validation, filter parsing, label rendering, grouping/sorting, and truncation ordering.
LSP Client Method src/lsp/client.rs	RustAnalyzerClient::inlay_hints async method sends textDocument/inlayHint request for a given Range, returning Vec<InlayHint> or empty vector on null response.
MCP Tool Integration & Orchestration src/ra/mod.rs, src/server/mod.rs, src/tools.rs	ra_inlay_hints tool resolves file from workspace, reads source lines, validates max hints and kind filters, computes request range, fetches hints from rust-analyzer, formats output (optionally with raw hints), aggregates notes, and reports truncation; module wiring and re-export formatting; tool instructions updated to clarify readonly vs. workspace-mutation semantics for ra_* tools.
Documentation & Integration Tests README.md, tests/integration_basic.rs	README documents new tool parameters, LSP UTF-16 positioning, truncation behavior, and removes inlay hints from Phase-Two Ideas; smoke test polls for successful hints requests; error-handling test asserts unknown kind rejection before server request; tools/list test expectations updated.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

A rabbit hops through lines of code,
Requesting hints along the road,
With kind filters and truncation's grace,
Inlay hints now have their place! 🐰✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 63.64% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Add rust-analyzer inlay hints tool' directly and clearly describes the main change: introduction of a new MCP tool for rust-analyzer inlay hints. It is specific, concise, and accurately reflects the primary objective of the pull request.
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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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/ra-inlay-hints-clean

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 4 additional findings in Devin Review.

[devin-ai-integration]

🟡 Empty kinds array silently filters out all inlay hints instead of returning all

When the user passes "kinds": [] (an empty array), parse_kind_filters at src/ra/inlay_hints.rs:68-86 returns Ok(Some(BTreeSet::new())) — a Some wrapping an empty set. In format_inlay_hints at src/ra/inlay_hints.rs:136-140, the filter check filters.map(|f| f.contains(...)).unwrap_or(true) will always return false for Some(empty_set), silently discarding every hint. This is semantically different from omitting kinds entirely (None), which correctly returns all hints. A user or agent passing "kinds": [] likely intends "no filter" (all kinds) but gets zero results with no error or warning.

Suggested change

	let Some(kinds) = kinds else {
	return Ok(None);
	};
	let Some(kinds) = kinds.filter(|k| !k.is_empty()) else {
	return Ok(None);
	};

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