Document agent self-setup for assigned identities

[dimavrem22]

Executive Summary

This PR documents how an agent can safely configure the Codex plugin with a human-assigned Inkbox identity.

• Inspects and runs the same downloaded installer artifact with the setup wizard disabled.
• Uses the complete non-interactive bootstrap command while preserving the assigned identity.
• Covers resumable human actions, error recovery, credential hygiene, and doctor verification.

Description

The README self-setup guide now walks an agent through downloading the official installer to a temporary file, inspecting it, and executing that exact file with --no-setup. It then documents the complete inkbox-codex bootstrap invocation with quoted placeholders and the project directory, Voice AI, signing-key rotation, and gateway startup options.

The guide also explains secret-safe credential handling, assigned-identity reuse, resumable requires_human and error results, and final verification with inkbox-codex doctor.

Reason

Agents given an existing identity and credential need a safe, executable path to finish setup without opening the interactive wizard or accidentally creating a replacement identity.

Decisions

• Installer integrity: Download, display, and execute one temporary installer artifact so the reviewed script is the script that runs.
• Identity continuity: Require retries to reuse the same assigned handle so partial setup remains resumable and does not create identity drift.
• Credential handling: Keep bootstrap credentials out of arguments and project files while allowing the plugin to persist only its scoped user configuration.

Testing

• Installer and CLI command contracts: bash install.sh --help, python3 -m inkbox_codex.cli bootstrap --help, and python3 -m inkbox_codex.cli doctor --help completed successfully and exposed the documented setup surface.
• README shell examples: all 12 Bash blocks passed bash -n, including the quoted identity and URL placeholders.
• Assigned-identity bootstrap and doctor behavior: pytest -q tests/test_bootstrap.py tests/test_doctor.py passed all 5 tests, confirming the focused bootstrap recovery and diagnostic behavior remains intact.
• Documentation diff: git diff --check passed with only README.md changed.