chore(caveman): purge plugin + always-on integration

Disable + uninstall caveman@caveman and delete every repo dependency on
it: SessionStart/UserPromptSubmit hook blocks, standalone hook files,
settings.json enabledPlugins + marketplace entries, install-plugins.sh
STEP 5.5, update-all.sh refresh step, plugins.lock.json entry, doctor.sh
checks, lib/detect-plugins.sh helpers, lib/profile.sh + plugin-advisor +
skills/profile protected-list entries, .gitignore runtime-file block,
and README/USAGE docs. Dead /caveman:compress refs replaced with
manual/claude.ai guidance. Memory-registry terse-format convention kept
(separate subsystem). Version 3.4.0 -> 3.5.0.

On a subscription plan caveman's ~75% output-token compression has no
cost benefit, and the always-on hooks added friction on validation
gates and client deliverables.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01X3e8LaH2vymmxyh36h3jFU

.gitignore

@@ -72,18 +72,6 @@ skills/find-skills
 # Staging area used by lib/toggle-external.sh when disabling a tool
 skills-disabled/
 
-# Caveman runtime hook files — deployed by caveman hooks/install.sh into
-# ~/.claude/hooks/ (which is a symlink to this repo's hooks/), so they
-# materialize here. They are user-scope state, not repo source.
-hooks/caveman-activate.js
-hooks/caveman-config.js
-hooks/caveman-mode-tracker.js
-hooks/caveman-stats.js
-hooks/caveman-statusline.sh
-hooks/package.json
-hooks/package-lock.json
-hooks/node_modules/
-
 # Local project config (per-machine, not shared)
 .claude/*
 !.claude/tasks/
@@ -95,9 +83,6 @@ hooks/node_modules/
 .claude/agent-memory/
 .claude/gstack/
 
-# Caveman compress backups — generated by /caveman:compress, recoverable via git
-*.original.md
-
 # Generated outputs
 graphify-out/
 .ctx7-cache/