docs: establish diagnostic contract and rule catalog SSOT (#7)

[mao2009]

Issue #7: Establish diagnostic contract and rule catalog SSOT

Refs #7

v1.0.0 で公開する Diagnostic の ID・カテゴリ・既定 severity・対象・説明を単一の SSOT として確定します。

Changes

docs/DIAGNOSTICS.md（新規・SSOT）

• RT/LVP/FIF の全 7 Diagnostic を棚卸しし、ID / category / title / message / default severity / 対象条件 / 説明を確定
• v1.0 公開契約の範囲を明示
  • 契約対象: ID / category / default severity / 既定有効であること
  • 契約対象外: title・message・description の文言および翻訳、実装クラス、検出の実装方式
  • 文言を契約から除外したのは、可読性改善と翻訳作業が破壊的変更にならないようにするためです。利用者は message ではなく ID で照合します
• ID 命名規則: PREFIX + 4桁連番。番号は削除後も再利用しない。prefix は analyzer クラスではなく rule family を表す（LVP0003 は ImmutableNamingSuggestionAnalyzer が emit するが LVP family）
• category 方針: Purity / FluentIf は既定 Error、Naming は既定 Warning 以下で既定ではビルドを止めない
• 互換性ルール: 追加・変更・削除を major/minor 別に定義。descriptor 変更時に同一コミットで更新すべきチェックリスト付き

ImmutableNamingSuggestionAnalyzer.cs（バグ修正）

LVP0003 の descriptor が description に FIF0001_Description を参照していました。DiagnosticResources には LVP0003_Description が存在しており、利用者には ID・category・severity が正しく見えるまま、説明文だけが FluentIf の内容になっている状態でした。

Issue #7 スコープの「Diagnostic descriptor と公開ドキュメントの不一致を解消」に該当します。新規 Analyzer rule の実装ではないため非スコープには抵触しません。

README.md

Diagnostic 表から docs/DIAGNOSTICS.md への参照を追加。README の表は要約、完全な契約は SSOT 側に置きます。

Verification

• descriptor が自身の ID の resource key を参照しているかを全 analyzer に対して機械的に検査 → mismatch 0 件（修正前は LVP0003 の 1 件）
• README の表と実装の ID / category / default severity の一致を確認
• Build: PASS (0 error)
• Tests: 56/56 PASS
• git diff --check: PASS

Issue #7 完了条件

• 全 Diagnostic ID が一覧化されている
• ID/category/title/message/default severity が確定している
• README と実装が一致している
• v1.0 で公開契約とする Diagnostic が明示されている
• 新規 ID・既存 ID 変更の方針が文書化されている

Batch context

Issue #18 の Batch Skill dogfood の一環として、#7–#10 を直列で実行しています。#7 は #8（回帰テスト）が対象とする「公開 Diagnostic」の定義を与えるため先行します。

Merge boundary

技術検証を通過しても MERGE CANDIDATE にとどまります。merge には Merge Skill による検証と、この PR / HEAD に対する新しい明示的 human approval が必要です。PR #19 の承認は再利用できません。

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation

  • Added an authoritative diagnostic reference covering supported diagnostics, contracts, severity, categories, compatibility rules, and naming conventions.
  • Updated README diagnostic titles to match the diagnostic catalog.

• Bug Fixes

  • Corrected the description associated with the LVP0003 diagnostic.

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ℹ️ Recent review info

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📒 Files selected for processing (1)

• README.md

🚧 Files skipped from review as they are similar to previous changes (1)

• README.md

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📝 Walkthrough

Walkthrough

The PR adds the diagnostic contract catalog, aligns seven README diagnostic titles with the catalog, and corrects the description resource used by diagnostic LVP0003.

Changes

Diagnostic contract

Layer / File(s)	Summary
Diagnostic contract documentation docs/DIAGNOSTICS.md, README.md	The catalog defines seven diagnostics, their metadata, analyzer ownership, naming rules, category policies, compatibility rules, and consistency requirements. README diagnostic titles now match the catalog wording.
Descriptor resource correction src/PureSharp.Core/ImmutableNamingSuggestionAnalyzer.cs	The LVP0003 descriptor now uses LVP0003_Description instead of FIF0001_Description.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 44bc4

This change documents the diagnostic contract, aligns README titles, and corrects the LVP0003 description resource reference. The supplied validation indicates the catalog and implemented descriptors are consistent, with no remaining merge-blocking risk.

🚥 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 clearly summarizes the main change: establishing the diagnostic contract and rule catalog as the single source of truth. It is concise and related to the pull request.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 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.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/issue-7-diagnostic-ssot

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@docs/DIAGNOSTICS.md`:
- Around line 231-236: Align the seven diagnostic title cells in README.md with
the corresponding catalog entries, including updating RT0001 to the catalog’s
title; alternatively, rename the README column to Summary if it intentionally
contains differing text. Preserve agreement between the README table and the
diagnostic catalog.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 8dbc4304-397c-457c-aacb-6b6559a91da2

📥 Commits

Reviewing files that changed from the base of the PR and between e099d62 and f1cc5b3.

📒 Files selected for processing (3)

• README.md
• docs/DIAGNOSTICS.md
• src/PureSharp.Core/ImmutableNamingSuggestionAnalyzer.cs

Included review availability: Your plan provides up to 8 included reviews per hour; 5 remain after this review.