Support URL-encoded JSON state, accept file input, rename browse→open, and show help when no args

[manabeai]

Motivation

• Simplify and standardize input handling by dropping compressed v2./base64/gzip decoding and only supporting URL-encoded JSON state values.
• Improve CLI UX so running rt with no arguments shows help rather than error, and rename the browse subcommand to a clearer open action.
• Allow users to pass a file path containing the link/state value to the CLI for convenience.

Description

• Replace v2./base64/gzip decoding with URL-decoded JSON handling in src/link_state.rs so state is treated as URL-encoded JSON only and decode_state just returns the URL-decoded string.
• Add arg_required_else_help = true to the clap Cli definition and rename the Browse subcommand to Open in src/main.rs to make rt show help when invoked without arguments and to use rt open to open the editor URL.
• Add resolve_input helper in src/lib.rs to detect when the link_or_state argument is a file path and read its (trimmed) contents, and introduce a ReadInputFile error variant for read failures.
• Update tests in tests/cli.rs to reflect URL-encoded JSON inputs and add input_file_is_accepted to verify file-path input handling.
• Update README.md examples to show URL-encoded JSON, the open subcommand, and file input usage.

Testing

• Ran cargo test (unit and integration tests) after changes and all tests passed successfully.
• Ran cargo build --release which completed successfully.
• Updated and ran CLI integration tests in tests/cli.rs, including the new input_file_is_accepted test, which passed.

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[chatgpt-codex-connector]

Decode URL state exactly once

When the input is a full URL, extract_state already returns a decoded query value via url.query_pairs(), but decode_state unconditionally applies urlencoding::decode again. This double-decoding breaks valid states that contain literal percent sequences: for example %25 in JSON becomes % after query parsing and then either errors (invalid URL encoding) or is transformed again (e.g. %2F -> /). As a result, some valid share links fail only in URL form while the same state string works directly.

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