docs: 2026-09-30 session save -- VAL conversions + long->int narrowing

Consolidates v3-val-conversions: 148/148, fixpoint OK (2,320,770
bytes). Records the conversion matrix, the Conversions simplification,
the new test, and remaining polish.

docs/summary_session-2026-09-30.md

@@ -0,0 +1,59 @@
+# Session save — 2026-09-30: VAL conversions + long→int narrowing
+
+Suite **148/148**; self-hosting fixpoint **OK**
+(`bootstrap/fixpoint.sh`, image **2,320,770 bytes**). `master`, tree
+clean except the user's uncommitted `compiler/toto.mod`.
+
+A short session: the remaining numeric conversion gap.
+
+## Step, tag and commit
+
+| Step | Tag | Commit | What |
+| --- | --- | --- | --- |
+| VAL conversions | `v3-val-conversions` | `1c774a7` | INTEGER/LONGINT/REAL conversions + long→int narrowing |
+
+## What
+
+`VAL` previously accepted only same-class operands and emitted **no**
+conversion code.  It now covers:
+
+| From → To | Codegen |
+| --- | --- |
+| `INTEGER` → `LONGINT` | `extsw` |
+| `LONGINT` → `INTEGER` | `copy w` (low 32 bits) |
+| `INTEGER` → `REAL` | `swtof` |
+| `LONGINT` → `REAL` | `sltof` |
+| `REAL` → `INTEGER` / `LONGINT` | `dtosi` (truncate toward zero) |
+
+Ordinal↔ordinal, pointer↔pointer and REAL↔REAL were already allowed.
+New `QbeGen` helpers: `NarrowLong`, `ConvRI`, `ConvRL`, `ConvLR`
+(alongside `WidenLong`/`ConvIR`).
+
+## Payoff
+
+`Conversions` is simplified: `StrToInt`/`StrToCard` accumulate in a
+`LONGINT` and range-check, then narrow with `VAL(INTEGER, v)` /
+`VAL(CARDINAL, v)`; the old "detect overflow before the 32-bit wrap"
+hand-guard is gone.
+
+## Tests (148)
+
+New: `t_valconv` (15) — int→long→int round-trip, int→real, real→int
+truncation, long→real.  `ConvProg`/`ConvResultsProg` still pass.
+
+Docs: `docs/summary_val-conversions.md`.
+
+## Resume
+
+```sh
+cd .../m2compiler-V3
+./bootstrap/fixpoint.sh                       # FIXPOINT OK
+cd compiler && ./build.sh && ./run_tests.sh   # 148/148
+```
+
+## Remaining polish
+
+- Multiple parents for `CLASS` (deliberate exclusion).
+- More stdlib: `SysClock`, richer `Strings` (`Insert`/`Replace`/
+  `Capitalize`), more `Math`.
+- Deeper variant-record / `IOChan` support.