[Lean Squad] feat(fv): Task 2 — informal spec for CommandLineParseResult.Equals

[Evangelink]

Extract a precise informal specification for CommandLineParseResult.Equals, the structural-equality implementation for the command-line parse result type.

The spec documents:

• 19 properties across 6 groups (null-safety, extensionality, object.Equals consistency, order-sensitivity, Empty-value behaviour, ToolName comparison)
• Algorithm walkthrough (O(n·m), pure, no exceptions for null input)
• Edge cases: null other, case-sensitive ToolName, order-sensitive errors/options
• Lean modelling plan: Option String for nullable, List for collections

Next: Task 3 — write ArgumentArity.lean (highest priority Lean target)

🔬 Lean Squad — automated FV agent

Fixes #7911

[Copilot]

Pull request overview

Adds an informal, source-derived specification for Microsoft.Testing.Platform.CommandLine.CommandLineParseResult.Equals, to support the Lean Squad FV workflow and future Lean modelling work.

Changes:

• Introduces a new FV spec markdown document describing CommandLineParseResult.Equals.
• Documents equality properties (null-safety, extensionality, order-sensitivity, Empty behavior, ToolName comparison) and an algorithm walkthrough.
• Captures Lean modelling notes/approximations for translating the behavior into Lean.

Show a summary per file

File	Description
formal-verification/specs/commandlineparseresult_equals_informal.md	New informal spec for CommandLineParseResult.Equals intended as input to Lean formalisation.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 6

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (1)

formal-verification/specs/commandlineparseresult_equals_informal.md:162

• The statement that Equals models whether the command line was “exactly the same string” is not accurate for this type: the parser normalizes option prefixes (trims -/--) and may unescape/strip quotes in arguments, so distinct command-line strings can produce equal parse results. Consider rephrasing this as “exactly the same parsed/normalized structure” to match the actual semantics.

The equality is **order-preserving structural equality** over the full parse tree. This mirrors the semantics of a command-line invocation: `--foo bar --baz` is semantically different from `--baz --foo bar` even if both produce option sets that "contain" the same options.  

This contrasts with `IsOptionSet` and `TryGetOptionArgumentList`, which are lookup methods that aggregate over all options with a matching name and are case-insensitive. The `Equals` method deliberately models "was the command line *exactly* the same string?", not "do both command lines select the same options?".

• Files reviewed: 1/1 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1