docs: L7 session re-emit works for small sessions; AST-arena blocks the compiler

docs/summary_lower_l7.md

@@ -31,28 +31,43 @@ flip once the inline emit is removed.
 Still scaffolding (inline emit untouched); suite **200/200**, FIXPOINT OK
 (3,401,129 bytes).
 
-## Gaps found (all fixable, all required for the flip)
-
-1. **`DefUnit` builds no AST.**  Its `ConstBlock/TypeBlock/VarBlock/
-   ProcHeading` loop never `AstAppend`s, so a definition module's AST has
-   no decls; its proc *headings* (which consume backend temps) cannot be
-   replayed.  Fix: append to `astDecl` in `DefUnit`.
-2. **Owned-table size.**  `MaxProc=64` / `MaxSym=512` are sized for one
-   unit; a full-session re-emit needs every module's procs/vars.  Growing
-   them grows the compiler image (watch the 4 MiB `sessBuf`).
-3. **Nested-module globals.**  `QualNode(outer, name)` does not see a
-   nested scope's non-exported globals; `ReenterGlobals` re-enters them
-   but with `curMod = -1` (empty `mod`), so `GlobalRef` falls back to
-   `$name` instead of `$<outer>_<name>`.
-4. **Definition-module proc replay** must emit only the heading
-   (`BeginFunc`/`FuncParam`/`AbortFunc`), like `LowerMethodHeadings`.
-5. Possibly more, revealed once a full session is compared.
-
-## Plan
-
-1. Fix (1) and (4); grow tables (2) within the image budget.
-2. Compare `Lower.LowerSession`'s image against the legacy session image
-   for the compiler's own sources (the real test).
-3. Fix the remaining gaps until the session image byte-matches.
-4. Flip: remove the inline emit; keep `Lower` per unit; the fixpoint
-   becomes the gate.
+## Progress (`ce2fc67`, tag `v3-lower7-session`)
+
+- **`DefUnit` now builds an AST** (proc headings recorded as
+  `NkProcDecl`); `LowerDecls` replays a bodyless proc as a heading.
+- **Session re-emit works** for small sessions: `lower_ok_files` added,
+  and `DBasicProg`, `DQualProg`, `TQual` (def-CONST), `TQualP`
+  (def-PROC) byte-match.  Fixes: image named after the program module;
+  `MaterializeGlobals` also materializes TYPE/CLASS names;
+  `SymTab.ReenterModGlobal` keeps nested-module globals'
+  `"<outer>_<name>"` symbols; `AST.Init` once per session under `-lower`.
+
+Suite **204/204**; FIXPOINT OK (3,405,813 bytes).
+
+## Remaining gaps
+
+1. **AST-arena size (fundamental).**  `LowerSession` needs every unit's
+   AST alive at once, but `AST.MaxNodes = 65536` is sized for one unit;
+   the compiler's session overflows it (`MakeNode` → `NoNode`, later
+   units dump `(nil)`).  Growing the arena past the 4 MiB `sessBuf` is
+   not viable.  So the session re-emit **cannot** handle the compiler —
+   the flip must instead emit **per unit** at each unit's END (AST valid,
+   scope open), which is the two-state / inline-emit-removal problem.
+2. **External procs.**  `storage_prog` differs: Lower emits
+   `$malloc_6(l link, ...)` where the legacy emits `$malloc(...)` — the
+   `ext` flag in `Lower.NoteProc` is hardcoded `FALSE` and `Mangled`'s
+   `ProcLink` fails after scopes close.
+3. Definition-module proc replay (done), nested globals (done).
+
+## Plan (revised)
+
+The session re-emit is a useful *verification* tool for small sessions,
+but the flip needs per-unit emission.  Concretely:
+
+1. Fix the external-proc flag (`NoteProc` should record `IsExternal` at
+   the EXTERNAL arm, not at the heading).
+2. Decide the flip mechanism: **two `QbeGen` states**, or remove the
+   grammar's inline `QbeGen` calls.  Either is a big, non-incremental
+   change; the fixpoint is the gate.
+3. Then `Lower` runs per unit (AST valid, scope open), which also makes
+   the external-proc and module-level resolution work naturally.