chore: reorganize examples

[tisonkun]

No description provided.

[Copilot]

Pull request overview

This PR reorganizes the examples from exn/examples to a new examples workspace member with sources in examples/src. This restructuring consolidates dependency management through workspace-level configurations and updates the build tooling accordingly.

Key Changes:

• Moved examples from exn/examples/ to examples/src/ as a new workspace member
• Centralized dependency versions in workspace configuration
• Updated xtask to reference the new examples directory structure and explicitly use nightly toolchain for formatting/linting

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Cargo.toml	Added examples to workspace members and introduced workspace-level dependency management
examples/Cargo.toml	New manifest defining the examples package with proper example targets
examples/src/*.rs	Updated file path references in comments from exn/examples/ to examples/src/
exn/Cargo.toml	Migrated to workspace dependencies and removed derive_more (now in examples)
xtask/Cargo.toml	Migrated to workspace dependencies
xtask/src/main.rs	Updated examples directory path and added explicit +nightly to cargo fmt/clippy commands
.github/workflows/ci.yml	Updated to actions/checkout@v6 and added nightly to test matrix
Cargo.lock	Reflects dependency updates including new transitive dependencies from insta upgrade

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