rename: uncommonlisp -> lumbda throughout the repo

Historical internal name "uncommonlisp" retired in favor of the
public name "lumbda" ahead of lumbda.com going live. Scope of
this commit:

Source files renamed:
  uncommonlisp.py                     -> lumbda.py
  asm/uncommonlisp.s                  -> asm/lumbda.s
  c/uncommonlisp.h                    -> c/lumbda.h
  whitepaper/uncommonlisp-whitepaper  -> whitepaper/lumbda-whitepaper (.rst + .pdf)

Binaries renamed (tracked ones; c/ was always gitignored):
  asm/uncommonlisp, asm/uncommonlisp-gc, asm/uncommonlisp.o,
  asm/uncommonlisp-gc.o                -> asm/lumbda(-gc)(.o)
  c/.gitignore                          -> ignores lumbda

Internal string updates (sed pass ordered longest-first):
  asm/uncommonlisp -> asm/lumbda
  c/uncommonlisp   -> c/lumbda
  uncommonlisp.py  -> lumbda.py
  UNCOMMONLISP_BIN -> LUMBDA_BIN (asm/test.sh env var)
  "uncommonlisp> " -> "lumbda> " (asm REPL prompt baked into binary)
  UNCOMMONLISP     -> LUMBDA (macros, comments)
  uncommonlisp     -> lumbda (prose)

Binary portal magic updated:
  "ULPORTAL" -> "LUMBDAB1"   # "Lumbda Binary v1"
Old portal files are not backward-compatible — this is a deliberate
break since it's the rename moment. S-expression portals already
carry their own ";; lumbda-portal v1" header and remain cleanly
versioned.

WHITEPAPER.pdf / WHITEPAPER.rst symlinks repointed to the renamed
files. Makefile's whitepaper target targets lumbda-whitepaper.pdf.

Not changed (intentional, separate phases):
  - Filesystem directory /home/fox/git/uncommonlisp itself
    (fox renames locally and the gitlab repo URL in a follow-up)
  - tests.py hardcoded cwd=/home/fox/git/uncommonlisp
    (matches the current on-disk location; will flip when the
    directory rename ships)
  - Git history (immutable; old commits still say uncommonlisp,
    which is correct — that's what they were)

Verified:
  137 asm no-GC + 137 asm GC + 571 Python + 83 C + 189 shared
  functional tests all pass under the new names.
  bench-gc-http (2000 req): all 4 cells behave as expected
  (cells 1/2 flat, 3 leaks, 4 bounded at 1 chunk).
  Python REPL, C REPL, asm REPL all start cleanly.

asm/Makefile

@@ -1,20 +1,20 @@
-all: uncommonlisp uncommonlisp-gc
+all: lumbda lumbda-gc
 
-uncommonlisp: uncommonlisp.s
-	as --64 -o uncommonlisp.o uncommonlisp.s
-	ld -o uncommonlisp uncommonlisp.o
+lumbda: lumbda.s
+	as --64 -o lumbda.o lumbda.s
+	ld -o lumbda lumbda.o
 
-uncommonlisp-gc: uncommonlisp.s
-	as --64 --defsym GC_NAIVE=1 -o uncommonlisp-gc.o uncommonlisp.s
-	ld -o uncommonlisp-gc uncommonlisp-gc.o
+lumbda-gc: lumbda.s
+	as --64 --defsym GC_NAIVE=1 -o lumbda-gc.o lumbda.s
+	ld -o lumbda-gc lumbda-gc.o
 
-test: uncommonlisp
+test: lumbda
 	@bash test.sh
 
-test-gc: uncommonlisp-gc
-	@UNCOMMONLISP_BIN=./uncommonlisp-gc bash test.sh
+test-gc: lumbda-gc
+	@LUMBDA_BIN=./lumbda-gc bash test.sh
 
 clean:
-	rm -f uncommonlisp.o uncommonlisp uncommonlisp-gc.o uncommonlisp-gc
+	rm -f lumbda.o lumbda lumbda-gc.o lumbda-gc
 
 .PHONY: all test test-gc clean

asm/lumbda.s

@@ -1,4 +1,4 @@
-# uncommonlisp.s — A Scheme interpreter in pure x86_64 assembly
+# lumbda.s — A Scheme interpreter in pure x86_64 assembly
 # No C. No libc. Just Linux syscalls and machine instructions.
 #
 # Value representation (tag in low 3 bits):
@@ -207,7 +207,7 @@
 .data
 # ============================================================
 
-prompt_str:     .ascii "uncommonlisp> "
+prompt_str:     .ascii "lumbda> "
 .equ prompt_len, . - prompt_str
 
 newline_ch:     .byte 10
@@ -351,7 +351,7 @@ s_hashset:      .ascii "#<hash-set>"
 err_ht_miss:    .ascii "Error: hash-table-ref: missing key\n"
 .equ err_ht_miss_len, . - err_ht_miss
 
-portal_magic:   .ascii "ULPORTAL"
+portal_magic:   .ascii "LUMBDAB1"
 .equ PORTAL_MAGIC_LEN, 8
 .equ PORTAL_HDR_SIZE, 48  # magic(8) + heap_size(8) + heap_base(8) + r14(8) + r15(8) + reserved(8)
 

asm/test.sh

@@ -10,7 +10,7 @@ cd "$(dirname "$0")"
 
 PASS=0
 FAIL=0
-UL="${UNCOMMONLISP_BIN:-./uncommonlisp}"
+UL="${LUMBDA_BIN:-./lumbda}"
 
 check() {
     local name="$1" input="$2" expected="$3"
@@ -28,7 +28,7 @@ check() {
 }
 
 echo "═══════════════════════════════════════════════════════"
-echo "asm/uncommonlisp test suite"
+echo "asm/lumbda test suite"
 echo "═══════════════════════════════════════════════════════"
 
 # ─── UNIT TESTS: individual primitives ────────────────────
@@ -205,7 +205,7 @@ EOF
 check "load-proc"  "(load \"$LOAD_TMP/b.lsp\") (square 9)" "81"
 
 echo "[unit] load — missing file returns #f"
-check "load-missing" "(load \"/tmp/__nope_uncommonlisp_$$\")" "#f"
+check "load-missing" "(load \"/tmp/__nope_lumbda_$$\")" "#f"
 
 echo "[unit] load — empty file is void"
 : > "$LOAD_TMP/empty.lsp"