Add generic WithContext error

[maxwase]

Also WithPath and experimental Path display wrapper

[Copilot]

Pull request overview

Adds a generic WithContext<C, E, F> error wrapper that pairs an error with a context value and renders both via a static ContextFormat strategy (Colon by default, PathColon for path-aware contexts, plus a WithPath alias). Also introduces an experimental DisplayPath newtype, a new with_context example, README documentation, and conditional no_std doc handling in lib.rs.

Changes:

• New WithContext<C, E, F> type with ContextFormat strategy trait, Colon/PathColon strategies, WithPath alias, and Error::source that skips the inner error to avoid duplication in chain walks.
• New experimental DisplayPath<T> adapter and an end-to-end example showing nested WithContext layers used with MainResult/thiserror.
• README section documenting WithContext/WithPath and a lib.rs tweak that switches between the README doc and a short fallback depending on the std feature.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/with_context.rs	Introduces WithContext, ContextFormat, Colon/PathColon strategies, aliases, and tests.
src/path_display.rs	Adds experimental DisplayPath<T> newtype adapting Path-like values to Display.
src/lib.rs	Registers new modules/re-exports and gates the README doc on the std feature.
examples/with_context.rs	End-to-end example combining nested WithContext with MainResult and thiserror.
README.md	Adds "Adding context" section documenting WithContext/WithPath; minor rewording elsewhere.
Cargo.toml	Marks the new with_context example as requiring the std feature.

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