Define minimal-token AI-to-AI dialogue protocol in README

[Copilot]

This PR introduces a compact, implementation-ready protocol for AI-to-AI exchanges optimized for minimal token usage. It standardizes message shape, payload constraints, and encoding/error semantics to reduce ambiguity across agents.

• Protocol frame + semantics

  • Defines canonical line format: T|id|k|payload
  • Documents k kinds (Q, A, C, S, E) and turn-level constraints (single objective/result/next step)
  • Clarifies id progression and rollover behavior (INT32_MAX boundary with explicit rollover signal)

• Payload contract

  • Establishes compact key/value convention with core keys (obj, res, err, next)
  • Adds extension rule for new keys via keydef=<chiave>:<significato> in the first S message of the task
  • Tightens parsing expectations with explicit delimiter usage and compact syntax

• Deterministic encoding + fallback behavior

  • Specifies percent-encoding for reserved/control characters (space, ;, |, =, :, %, newline, carriage return, tab)
  • References RFC3986 unreserved characters as cleartext-safe
  • Defines ambiguity fallback message (E|err=ambiguous;next=clarify)

• Executable examples

  • Adds concrete message examples for Q/A/C/S and detail-request pattern

T|17|Q|obj=test_scope;ctx=api_auth
T|18|A|res=2_fail;err=timeout;next=retry_1
T|19|C|act=run;cmd=pytest%20-k%20auth
T|20|S|res=pass;next=close

Original prompt

Protocollo per dialogo AI-to-AI a token minimi