chore: remove version.txt in cli/lib

[dsherret]

No description provided.

[dsherret]

In a way, the previous versioning was better because now this needs to be pinned.

[Copilot]

Pull Request Overview

This PR removes the version.txt file from cli/lib and transitions to using Cargo's built-in CARGO_PKG_VERSION environment variable for version management. This simplifies the version synchronization process by eliminating a separate version file and relying on the Cargo.toml version as the single source of truth.

• Replaced env!("DENO_VERSION") with env!("CARGO_PKG_VERSION") in version.rs
• Updated the release script to use setVersion() instead of writing to version.txt
• Added a lint check to ensure cli and lib crate versions stay synchronized

Reviewed Changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/release/01_bump_crate_versions.ts	Replaced version.txt writes with setVersion() calls and added conditional logic to skip incrementing deno_lib in the dependency loop since it's set explicitly to match cli version
tools/lint.js	Added ensureCliVersionMatchesLibVersion() function to verify version synchronization between cli and lib crates
cli/lib/version.txt	Removed the version.txt file (previously containing "2.5.6")
cli/lib/version.rs	Changed from custom DENO_VERSION env var to using CARGO_PKG_VERSION
cli/lib/build.rs	Removed build script code that read version.txt and set DENO_VERSION env var
cli/lib/Cargo.toml	Updated version from "0.39.0" to "2.5.6" to match cli version
Cargo.toml	Updated deno_lib dependency version to "=2.5.6" with exact version requirement
Cargo.lock	Updated deno_lib package version to "2.5.6"

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