docs: record L7 gap fixes and the remaining scoping blocker

CASE chunking, VAL, qualified calls, VAR actuals and proc values moved
the compiler-session divergence to AST.AddTxt; the next blocker is
Lower's flat symbol table colliding on common names across procedures.

docs/summary_lower_l7.md

@@ -158,3 +158,43 @@ tests and the suite are green; the fixpoint is green (`-lower` is not
 used there).
 
 Suite **204/204**; FIXPOINT OK (3,695,508 bytes), session 0 errors.
+
+---
+
+## Progress: more Lower coverage (`132a981`, tag `v3-lower7-gaps`)
+
+First divergence moved to `AST.AddTxt` (line ~6961).  Fixes:
+
+- **CASE chunking.**  The arm list was capped at `AST.MaxChild` (8):
+  `CaseStat`/`CaseAlt` appended arms with `SetChild(cnode, NChild, arm)`,
+  which silently drops beyond 8.  They now build a chunked arm sequence
+  (`AstAppend`, container kind `NkBlock`), and `LowerCase` follows the
+  continuation chunks.  This was the big `M2S.Get` gap.
+- **`VAL(T, e)`** in `LowerBuiltinExpr`, same widen/narrow/convert chain
+  as the grammar.
+- **Qualified calls** (`FileIO.ReadBytes`) resolve through Lower's proc
+  tables (SymTab's scopes are closed); `CalleeAlias` returns the base
+  name so the mangled symbol stays `<base>_<uid>`.
+- **VAR actuals.**  `LowerExprFull` records value→address with
+  `NoteAddr`, mirroring the grammar's `Design`; `AddrOfVal` could not
+  rely on the grammar's notes because its 256-entry ring wraps during a
+  whole-session emit.
+- **Bare proc values** (`CurrentCh := CharAt`): `Resolve` recognises the
+  proc table and `LowerProcAddr` emits the code address; sibling method
+  names fall through to the THIS-binding path.
+
+## Next blocker: symbol scoping
+`Lower`'s symbol table is a single **flat, latest-wins** table, so
+common names (`s`, `i`, `k`) collide across procedures.  E.g. `HIGH(s)`
+in `AST.AddTxt` (an open-array parameter) resolved to a fixed array of
+256 from another procedure.  `lower_ok` tests are too small to collide.
+
+Two ways forward:
+1. record a scope id per symbol and resolve within the active procedure
+   chain, or
+2. run `Lower` with `SymTab`'s scope open (the grammar-based call) and
+   resolve locals via `SymTab` first — the earlier attempt only broke
+   `EndModule`'s `ExitCode` lookup, fixable by materialising the program
+   globals in `EndSession`.
+
+Suite **204/204**; FIXPOINT OK (3,711,028 bytes), session 0 errors.