Define a verifiable core compatibility baseline for current plugins #102

Effort: L

Problem

Current plugin compatibility cannot be expressed reliably by the existing version strings. The tagged v0.3.0-alpha.1 predates several required APIs, and later checkouts reuse version strings (the current checkout reports 0.3.0-alpha.2). minHost is exposed as metadata by the plugin loader; no frontend enforcement was found in the inspected checkout.

Source-level dependency boundaries

• 0dcc913 (July 10): lib/dlc_paths.py and _resolve_dlc_path; required by current Lyrics Karaoke and Difficulty Ladder backends.
• d876ded (July 13): sloppak.read_member_bytes; required by Difficulty Ladder generation and Feedpakr pack reuse/upgrade/deduplication.
• 05be9eb (July 19): chart-transform capability; required for Chordr automatic diagram enrichment.
• 03e1c1d (July 22): /ws/sync/{session_id}; required for Splitscreen LAN sharing.
• f7c761c (September 16, this fork): renderFrameAt, renderFrame and setExternalFrameDriver; required by Visual Export and optional coordinated Splitscreen rendering.
• 7633211 (September 17, this fork): playerContexts and player-difficulty.v1; required for full per-player integration.
• e5339c0 (September 23, this fork): mastery selection by phrase tier number and getPhrases().top_difficulty; needed for current Difficulty Ladder presentation to agree with rendered tiers.

These are source/history findings, not an end-to-end certification of each historical build. Basic Piano and basic Splitscreen have their required APIs in the alpha.1 tag.

Proposed work

• Publish a distinct, traceable version for a supported baseline containing these APIs. e5339c0 or a tested descendant is a candidate common baseline, not an already-certified release.
• Document upstream-versus-fork requirements and pin exact commits until a release identifies the baseline.
• Define required versus optional host capability checks. Missing optional APIs should disable only their dependent features.
• Make minimum-host metadata actionable with clear diagnostics and prerelease-aware comparison; do not blindly enforce existing placeholder 1.0.0 values.
• Test representative plugin startup and feature paths against the declared minimum and latest host.
• Track Visual Export's existing reports: Declare the correct minimum host version feedback-plugin-visual-export#6 and No working minHost/splitscreen version to record — the splitscreen APIs this plugin calls don't exist feedback-plugin-visual-export#7.

Acceptance

A user can identify a compatible build from its release/commit, and an incompatible feature explains its missing requirement before use. Record tested host and plugin revisions in the compatibility matrix.