Align with current Pi core package and events

[nicabarnimble]

Summary

Align the Emacs adapter with current Pi core packaging and compaction RPC events.

Pi core has moved from the @mariozechner/* npm scope to @earendil-works/*, and current RPC compaction events are now unified as compaction_start / compaction_end for manual, threshold, and overflow compaction.

This PR updates the integration-test Pi package baseline, updates user-facing install guidance, and teaches the Emacs adapter to handle the current compaction event names while preserving legacy auto_compaction_* aliases.

Changes

• Update Pi install guidance from @mariozechner/pi-coding-agent to @earendil-works/pi-coding-agent in the README and missing-CLI warning.
• Update Makefile real-integration Pi package from hard-coded @mariozechner/pi-coding-agent to configurable PI_PACKAGE ?= @earendil-works/pi-coding-agent.
• Pin the default real-integration baseline to PI_VERSION ?= 0.75.4, the current Pi supply-chain hardening release.
• Install the cached integration-test Pi binary with npm install --ignore-scripts.
• Handle current RPC events:
  • compaction_start
  • compaction_end
• Keep legacy aliases working:
  • auto_compaction_start
  • auto_compaction_end
• Update compaction state/render/input tests to exercise the canonical current event names.
• Add explicit alias coverage for older Pi binaries.

Background

Relevant Pi core changes:

• 3e5ad67e in earendil-works/pi-mono: migrated Pi packages to the @earendil-works/* npm scope.
• 161ad182 in earendil-works/pi-mono: unified compaction UI/session events from auto_compaction_* to compaction_start / compaction_end.

Current Pi RPC docs list compaction_start / compaction_end and include a reason field of manual, threshold, or overflow.

Testing

Ran:

make setup-pi
make test-core
make test-input

make setup-pi installs @earendil-works/pi-coding-agent@0.75.4 with --ignore-scripts and verifies pi --version.

make test-core passes.

make test-input passes.

[nicabarnimble]

I amended the branch to keep this as a single focused commit after updating the package baseline to the current 0.75.4 hardening release and adding --ignore-scripts.

Reference: https://x.com/badlogicgames/status/2057108413113340039