docs: real How-it-works + worked example for v0.1.0

[corvid-agent]

Summary

The previous "How it works" section was the scaffold's generic "replace the starter bash stub with any language" paragraph — accurate for the template, meaningless for a published plugin. Replace with text that describes how bin/jwt actually operates.

What changed

• How it works now describes the real mechanics: base64url ↔ base64 conversion via tr '_-' '/+' plus padding, dual base64 -d / base64 -D fallback so it works on both Linux and macOS, pipe through jq for color JSON, and a one-liner about why the signature segment is intentionally not verified ("inspect, not trust").
• Install calls out the runtime deps (bash, jq, base64) and notes that fledge jwt ui opens the bundled HTML via open (macOS-first; Linux users can open the printed path).
• Usage gains a worked terminal-output example with the canonical John-Doe HS256 token so the README shows what you actually see, not just the command.
• Development points at bin/jwt directly instead of chmod +x bin/* (only one binary in this plugin) and includes the real ui test command.

No code or plugin.toml changes.

Test plan

• ./bin/jwt decode <sample> produces the output shown in the README
• ./bin/jwt (no args) prints the usage that matches the documented subcommands
• ./bin/jwt decode "not-a-jwt" errors with the format check (matches the no-signature-verification claim — only structural check happens)
• All claims about the bash internals (tr '_-' '/+', padding, base64 -d/base64 -D fallback, jq pipe) cross-checked against bin/jwt

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the README.md to provide more detailed information about the plugin's features, requirements, and internal workings. It includes specific examples of CLI output and clarifies platform-specific behavior for the web inspector. Feedback focuses on improving the readability of the installation instructions and providing a complete, valid JWT example for the usage section to ensure the documentation is actionable.

[gemini-code-assist]

The phrasing '(macOS — on Linux, ...)' is slightly awkward due to the nested dash. Using a semicolon or separate sentences would improve readability.

Suggested change

	Requires `bash`, `jq`, and `base64` on PATH. The `ui` subcommand opens the bundled HTML with `open` (macOS — on Linux, open the file path it prints in your browser).
	Requires bash, jq, and base64 on PATH. The ui subcommand opens the bundled HTML with open on macOS; on Linux, it prints the file path to be opened manually in a browser.

[gemini-code-assist]

The example JWT is truncated with ..., which makes the command invalid if copied and pasted. Providing a full, valid token allows users to test the command immediately and see the results described in the next section.

Suggested change

	fledge jwt decode eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIi...
	fledge jwt decode eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c