Commit tune maps and research so tunes are reachable from the phone

Removes the *.hex/maps_cache gitignore rule (explicit user call, reversing
the earlier no-redistribution stance) so the official TuneECU catalogue
maps, derived SAI/O2-delete composites, and the checksum/composition
tooling are actually available to pull up on a phone browser when using
the real TuneECU app. Also folds in tonight's KWP2000 fixes (TesterPresent
keep-alive, connect-failure cleanup, slow-init StartCommunication fix) and
the accumulated research docs.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FP2GaxS9HkUdL5sLBnjKje

tunie/research/reference-maps/PERMUTATIONS.md

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+# Full mechanical-odo Bonneville permutation grid — cross-diff (Aug 2026)
+
+Downloaded and cross-diffed every official mechanical-odo Bonneville
+calibration TuneECU ships for the exhaust x fuel grid (up to VIN 739050):
+stock production/aftermarket, Arrow 2-in-1, Arrow 2-in-2, each at E10 and
+E25, across both catalog batches (`t202`/`t203`). 12 files, all reconstructed
+to the flat 384 KB ROM with `reconstruct_rom.py` and diffed byte-for-byte.
+
+IDs used: `20187 20188 20191 20192` (stock), `20262 20263 20264 20265`
+(`t202` Arrow), `20313 20314 20315 20316` (`t203` Arrow).
+
+## t202 vs t203: same tune, reissued
+
+Every `t202`/`t203` pair with an identical catalogue description (e.g.
+`20262` vs `20313`, both "Arrow 2 in 1, E10") differs by only **10 bytes**,
+in two groups:
+
+- 8 bytes at `0x4FFFA-B/E-F` and `0x5FFFA-B/E-F` — right at the `0x50000`/
+  `0x60000` block boundaries, almost certainly per-block ID/checksum
+  metadata (consistent with `DEVICES.md`/`README.md`'s prior finding that
+  the `caXX` footer bytes are map-ID metadata, not a calibration checksum).
+- 2 bytes at `0x53626-27` — one real 16-bit calibration value changed. Small,
+  single-cell revision.
+
+**Conclusion: `t202` and `t203` aren't different calibrations, just a
+catalog-ID reissue with one tiny tweak.** Resolves the earlier open question
+("which of 20262 vs 20313 is correct for us") — it doesn't matter, use
+either.
+
+## Fuel delta (E10 -> E25) is real, consistent, and localized
+
+Matched pairs (same exhaust, VIN range, everything else equal, only fuel
+spec differs):
+
+| Pair | Exhaust | Diff |
+|---|---|---|
+| `20262` vs `20263` | Arrow 2-in-1 | 4809 bytes (1.22%) |
+| `20264` vs `20265` | Arrow 2-in-2 | 4562 bytes (1.16%) |
+| `20313` vs `20314` | Arrow 2-in-1 (t203) | 4809 bytes — **identical set** to `20262`/`20263` |
+| `20315` vs `20316` | Arrow 2-in-2 (t203) | 4562 bytes — **identical set** to `20264`/`20265` |
+| `20187` vs `20191` | stock production | only 60 bytes (0.02%) |
+
+The E10->E25 delta for Arrow 2-in-1 vs Arrow 2-in-2 overlaps 93% (4455 of
+4562-4809 bytes) — same fuel-table region touched regardless of exhaust,
+which is exactly what you'd expect (ethanol compensation lives in the fuel
+tables, not the exhaust-specific cells). The stock-production E10->E25 delta
+being tiny (60 bytes) while the Arrow one is ~80x larger is odd at first
+glance, but `20187` carries no VIN-range/fuel spec in its description at
+all — it and `20191` likely aren't a clean matched pair the way the Arrow
+E10/E25 pairs are (`20191` adds a VIN-range qualifier `20187` lacks). Treat
+`20262`/`20263` as the trustworthy E10-vs-E25 reference, not `20187`/`20191`.
+
+## Exhaust delta and fuel delta are NOT independent/disjoint
+
+Checked whether the "stock -> Arrow 2-in-1" delta and the "E10 -> E25" delta
+touch separate bytes (which would let us compose them by simple
+copy/overlay):
+
+- Exhaust delta (`20187` -> `20262`): 7548 bytes
+- Fuel delta (`20262` -> `20263`): 4809 bytes
+- **Overlap: 4149 bytes** — the large majority of the fuel delta's footprint
+  is inside the exhaust delta's footprint too.
+
+**This means naive delta composition (baseline + delta A's changed bytes +
+delta B's changed bytes) doesn't work cleanly** — both mods rewrite
+overlapping cells in the same VE/fuel tables (expected: richness-for-exhaust
+and richness-for-ethanol are both corrections to the same underlying fuel
+surface, so of course they land on the same cells). You can't just XOR two
+independent byte-level diffs onto a base map; you'd overwrite one mod's
+change with the other's rather than combining them. Real composition would
+need table-level math (read both as VE values, apply both corrections
+arithmetically), not byte-patching — a materially bigger undertaking than
+`toggle_devices.py`'s simple flag flip.
+
+## What this means for "build our own Arrow + SAI/O2-delete tune"
+
+**Good news:** the exhaust x fuel grid is *already solved* — TuneECU
+engineers already shipped the exact validated combination you want
+(`20262`/`20313`, Arrow 2-in-1, E10). No synthesis needed there; picking the
+catalog entry is strictly better than trying to reconstruct it from deltas.
+
+**Bad news, unchanged from `COMMUNITY_TUNING.md`:** none of these 12 files
+vary the SAI/O2-delete axis — TuneECU never shipped an Arrow-exhaust variant
+with devices off. The grid we now have doesn't help fill that gap, because
+the gap isn't on this grid. We're still bottlenecked on the single external
+`2009AIRBOXBONNY.hex` reference (not currently in the repo, needs
+re-fetching) for that axis, and even that reference conflates "no airbox"
+with "no SAI/no O2" in one diff (per `DEVICES.md`), which the exhaust-vs-fuel
+overlap finding above suggests may be a *real* problem, not just a
+theoretical one — table-level effects don't separate cleanly by simple
+byte diffing when two mods land on the same cells.
+
+**Revised recommendation:** don't try to hand-synthesize "Arrow 2-in-1 +
+real SAI/O2 delete" from byte deltas — the overlap finding shows that's not
+sound with the tooling we have (byte-diff, not semantic table-diff). Either:
+1. Decode the fuel tables to actual VE values (`table_map.py`/`TABLES.md`
+   already locate them) and do the composition arithmetically, cell by cell,
+   rather than at the byte level — a real project, not a script tweak.
+2. Or just use a real matched commercial tune (DNK, since TTP's storefront is
+   effectively defunct) rather than DIY-composing one.