Rewrite README to match updated product positioning

[George-iam]

Summary

• Complete README rewrite aligned with AXME Cloud positioning framework
• Hero: "Durable execution where agents, services, and humans coordinate as equals"
• Updated code snippet to agent listener pattern (listen, process, resume) instead of createIntent
• Added ScenarioBundle section with minimal JSON example and axme scenarios apply
• Added delivery bindings table (stream, poll, http, inbox, internal)
• Added human-in-the-loop section with 3 paths (CLI, email, form)
• Added agent addressing scheme (agent://org/workspace/name)
• Fixed SDK status: all v0.1.2 Alpha (was incorrectly showing GA/Beta)
• Fixed CLI install: curl installer (was go install)
• Fixed imports: correct package paths for all SDKs
• Updated lifecycle states to current model (CREATED through TIMED_OUT)
• Dropped axme-reference-clients (not a real repo yet)
• Changed spec repo references from axme-spec to axp-spec

Test plan

• Verify all GitHub links resolve correctly
• Verify code snippet syntax matches actual SDK API
• Confirm ScenarioBundle JSON matches axme-examples format
• Review tone and positioning against AXME_CLOUD_POSITIONING.md

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