docs: Archive historical documentation (26 files → doc/archive/)

Moved completed/historical docs to doc/archive/ for cleaner context:

Archived (26 files):
- Analysis docs: variable tempo, audio architecture, build optimization
- Handoff docs: 6 agent handoff documents
- Debug reports: shadows, peak meter, timing fixes
- Task summaries and planning docs

Kept (16 files):
- Essential: AI_RULES, HOWTO, CONTRIBUTING, CONTEXT_MAINTENANCE
- Active subsystems: 3D, ASSET_SYSTEM, TRACKER, SEQUENCE
- Current work: MASKING_SYSTEM, SPECTRAL_BRUSH_EDITOR

Updated COMPLETED.md with archive index for easy reference.

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/archive/PHASE2_COMPRESSION.md b/doc/archive/PHASE2_COMPRESSION.md
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+# Phase 2 – Compression & Size Reduction
+
+This document tracks ideas and strategies for the final optimization phase to reach the <=64k goal.
+
+## Executable Size
+
+### Windows
+- **Replace GLFW**: For the final build, replace the statically linked GLFW library with a minimal "tiny" implementation using native Windows API (`CreateWindow`, `PeekMessage`, etc.). This is expected to yield significant savings.
+  - *Status*: Deferred until feature completion.
+- **CRT Replacement**: Consider replacing the standard C runtime (CRT) with a minimal startup code (e.g., `tiny_crt` or similar) to avoid linking heavy standard libraries.
+- **Import Minimization**: Dynamically load functions via `GetProcAddress` hash lookup to reduce the Import Address Table (IAT) size.
+
+### General
+- **Shader Compression**: Minify WGSL shaders (remove whitespace, rename variables).
+- **Asset Compression**:
+  - Store spectrograms with logarithmic frequency bins.
+  - Quantize spectral values to `uint16_t` or `uint8_t`.
+  - Use a custom packer/compressor for the asset blob.
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