docs: pre-public visibility cleanup pass

[IamMrCupp]

Summary

Cleanup pass identified by the public-readiness audit so the planning repo can be flipped from private to public without surprises.

Redactions / safety

• SESSION_HANDOFF.md — Removed the home K8s cluster spec (5-node ARM64, 2Gbps fiber, Flux/HAProxy/MetalLB/nginx). Replaced with neutral "Self-hosted Kubernetes cluster" framing.
• IMPLEMENTATION_PLAN.md + DEPLOYMENT.md — Dropped references to the private Claude working-folder research-gui-framework.md (dead pointers for public readers); inlined a one-line summary instead.

Generalization

• SESSION_HANDOFF.md + README.md — Stripped Cowork / Claude Code / "future-Aaron" framing so a public contributor reads it naturally. Removed "Aaron's existing global Claude.ai instructions cover this" and reworded plan-approval guidance to target any contributor.

Fixes

• SESSION_HANDOFF.md — Flattened stale planning/*.md and research/*.md cross-references to bare filenames (repo layout has been flat since PR docs(readme): flat-layout document index + sync completed status items #7).
• IMPLEMENTATION_PLAN.md — Author email aligned to mrcupp@mrcupp.com (was aaron@mrcupp.com).
• PLAN_OF_ACTION.md — Reworded M4+ LumaNode line from "reverse-engineered" to "community-documented protocol or vendor cooperation" — friendlier framing before any vendor contact.
• SYNESTHESIA_OSC.md — Fixed stale synesthesia-monitor command in a code block; prose already said audiophore monitor.

Out of scope (judgment calls, deliberately not touched): M4+ "this is where revenue lives" framing in PLAN_OF_ACTION.md, and the competitor-product commentary in README.md.

Test plan

• Render the diff and skim the rewritten sections of SESSION_HANDOFF.md for tone
• Confirm lychee CI passes (no broken cross-references after flattening paths)
• After merge, flip the repo to Public in Settings