docs: CALC-COMPILE.md — record the session state for resuming tomorrow

No compiler change has been made yet; this line of work is still entirely at
the planning stage. Records the pre-CALC baseline that Stage 1 must not
break, verified on this commit rather than taken from a summary:

  ./tests/run_all.sh   -> OVERALL: ALL PASS   (~74 s)
  compile matrix       -> 56 passed, 0 failed (of 56)

Also records what was deliberately left undone: nonvacuity.sh was not
re-run (it is outside run_all.sh and must be run manually after touching
any check), the memory-mode compile behind Q6 is still untried, the two
reference .COM artifacts remain untracked, and the choice between the two
candidate layout fixes is flagged as the one decision not to defer past the
first sitting.

CALC-COMPILE.md

@@ -334,6 +334,30 @@ parallel:
 Ordering rule within the ladder: cheapest-and-most-independent first, then the
 ladder order (each stage removes the blocker the previous one exposed).
 
+### Session state — where to resume
+
+Last touched 2026-10-17. **No compiler change has been made yet**; this line of
+work is still entirely at the planning stage, and everything below is the
+*pre*-CALC baseline that Stage 1 must not break.
+
+- **HEAD** `ce7e8cd` (this document). Nothing pushed; `origin/master` is behind.
+- **Verified baseline, run on this commit:** `./tests/run_all.sh` →
+  **OVERALL: ALL PASS** (~74 s), and the compile matrix is **56/56**. Those are
+  the numbers Stage 1's ratchet must leave intact.
+- **Not re-run this session:** `tests/nonvacuity.sh` (78 ok / 0 failed at the
+  last run). It is not in the default `run_all.sh` and must be run **manually**
+  after touching any check.
+- **Still present and deliberately untracked:** `Resources/TP3/CALC.COM` and
+  `Resources/TP3/HELLO.COM`, the two reference binaries used for §3.1. They are
+  derived from the proprietary `TURBO.COM`; do not stage them. The recipe and
+  the numbers are in §3.1, which is what this document keeps.
+- **Cheap evidence still missing (Q6):** one memory-mode run of `TURBO` in
+  dosemu to see whether CALC reports "Compiler Overflow #99" as its banner
+  warns. The `.COM` path succeeds; the memory path was never tried.
+- **The one decision not to defer past the first sitting:** which candidate fix
+  to implement for §3 — match the original's orientation, or a dynamic data
+  base with fixups. Everything else in the stages below is mechanical.
+
 ### Next session
 
 **Stage 1 — the ratchet (§1).** Small. Lands the measuring device before the