Command 1.0.0: JSON Command Interpreter (#9)

[LK-Simon]

Summary

Implements #9 on top of the README enhancement branch and prepares ESPressio Command 1.0.0.

Feature

• adds representation-neutral CommandValue scalar values;
• evolves CommandInvocation::positional / named to retain native structured scalar types;
• preserves CommandContext::Raw() and adds CommandContext::Value();
• adds an explicit TextCommandInterpreter facade;
• adds optional JsonCommandInterpreter support backed by ArduinoJson 7.x;
• supports canonical path arrays or a convenience command string, named/positional scalar values, structured JSON results, independent parsing, and machine-readable Command discovery;
• keeps ArduinoJson out of the normal Command umbrella and required dependency graph.

Breaking interface change / version

This is prepared as 1.0.0 because the exact public types of CommandInvocation::positional and CommandInvocation::named change from string containers to CommandValue containers. Common string assignments/initializer lists remain supported, but code depending on those exact container types requires migration.

Validation

Tests cover existing textual behaviour, legacy string assignments, typed structured invocation, conversion/validation boundaries, middleware type preservation, malformed/ambiguous JSON, scalar constraints, result serialization, discovery metadata, hidden Command behavior, and existing registry/CommandLine behavior. CI also compiles the JSON adapter on ESP32 with ArduinoJson 7.4.x and retains the ESP32 Event-integration validation.

Documentation

README, full changelog, package/component version metadata and textual/graphical dependency documentation are updated for 1.0.0. The README preserves the restored/enhanced material and adds full JSON usage, discovery and 0.4.x -> 1.0.0 migration guidance.

This PR intentionally targets docs/7-readme-enhancements so feature reintegration can follow the pending documentation reintegration. Every feature commit references #9.