Add PLAN.md and TODO.md planning artifacts

PLAN.md: living 12-milestone roadmap from CONTEXT.md's build order,
each with a verify gate and its precision invariant; open questions
carried forward. TODO.md: near-term M0-M2 slice as ordered tasks.

TODO.md

@@ -0,0 +1,63 @@
+# TODO.md — near-term actionable slice
+
+The immediate, ordered tasks to execute the first step of `PLAN.md`: Milestone 0
+(transition) → Milestone 1 (`bank_model`) → Milestone 2 (`peaks`). Everything past
+M2 lives in `PLAN.md`, not here. Verify REAPER API names/flags against
+`vendor/reaper-sdk/sdk/reaper_plugin_functions.h` before use.
+
+## Now — Milestone 0: transition scaffold
+
+1. Delete the MPE modules: `src/mpe_model.{h,cpp}`, `src/mpe_view.{h,cpp}`,
+   `tests/test_mpe_model.cpp`.
+2. CMakeLists.txt — rename `project(reaper_mpeview …)` and the MODULE target to
+   `reaper_reasampler`; update `OUTPUT_NAME`, `PREFIX ""`, and the WIN32/APPLE/
+   Linux SUFFIX blocks to the new target name.
+3. CMakeLists.txt — replace the `mpe_model` static lib with a `bank_model` static
+   lib (`src/bank_model.cpp`, `PUBLIC src` includes); replace `mpe_model_tests`
+   with `bank_model_tests` (`tests/test_bank_model.cpp`), keep `add_test` / CTest.
+4. `src/main.cpp` — remove `#include "mpe_view.h"` and every `MpeView_*` call
+   (`MpeView_Toggle`, `MpeView_IsOpen`, `MpeView_OnTimer`, `MpeView_Cleanup`).
+   Leave a minimal, loadable extension entry that resolves API pointers and logs
+   to console; keep the `command_id`/`gaccel`/`hookcommand` registration pattern
+   as a commented seam for the future action family.
+5. `src/main.cpp` — replace the `CEREBELLUM_MPEVIEW_TOGGLE` action string with the
+   chosen sampler action-id prefix (record the prefix in a comment; it is
+   forever-stable once shipped).
+6. Confirm the tree still configures and builds:
+   `cmake -B build -S .` → `cmake --build build` → `ctest --test-dir build`.
+   (bank_model tests may be a single placeholder assertion at this point.)
+7. README.md — retarget the layout / "where to build next" sections to the
+   sampler module set so the first implementer is not misled by MPE prose.
+
+## Next — Milestone 1: bank_model + JSON round-trip (pure, no REAPER)
+
+8. `src/bank_model.h` — define `Sample` with the full field set from CONTEXT.md
+   §Data model (id, name, relative path, source mode, source range project-time +
+   PPQ, track GUID(s), wet/dry, channels, SR, length sec + beats, capture tempo,
+   optional key, peak/RMS/LUFS, clip flag, tier, content hash, provenance, ts).
+9. `src/bank_model.h/.cpp` — `BankIndex`: ordered, keyed by id; `add` / `remove` /
+   `query`.
+10. Dedup: content-hash lookup so an add with an existing hash collapses.
+11. Tiers: `scratch` | `archive`, tier-move, tier filtering; scratch auto-prunable.
+12. JSON serialize/deserialize to/from `std::string` (self-contained; no external
+    JSON dep unless one is already vendored — check first).
+13. Enforce **relative-paths-only** at the model boundary (reject/normalize
+    absolute paths on add).
+14. `tests/test_bank_model.cpp` — assert: full-field round-trip lossless; dedup
+    collapses equal-hash adds; tier move + filter correct; absolute-path rejected;
+    empty-index and malformed-JSON edge cases.
+
+## Then — Milestone 2: peaks (pure, no REAPER)
+
+15. `src/peaks.h/.cpp` — min/max bin computation from interleaved PCM for a target
+    bin count; per-channel (no silent fold). Add `peaks.cpp` to the `bank_model`
+    lib (or a sibling pure lib) so tests link it.
+16. `tests/test_peaks.cpp` (+ CTest entry) — assert: full-scale sine envelope ≈
+    ±amplitude per bin; ramp envelope monotonic; silence/DC → zero envelope;
+    short-buffer and non-divisible-length (remainder bin) edge cases.
+
+## Definition of done for this slice
+- `ctest --test-dir build` green with `bank_model_tests` and `peaks` tests present.
+- No `mpe`/`Mpe`/`MPE` symbols remain in `src/` or `tests/`.
+- The extension target builds under the new name and loads in REAPER (console log
+  on load); it registers no half-wired actions.