Compiler: accept unnumbered programs, fix string concat in PRINT

Three fixes that lift seven test programs from skipped to passing,
bringing the AOT compiler harness from 56/56 to 63/63.

- Unnumbered programs (compiler_main.c): src/compiler_main.c skipped
  any line that didn't start with a digit, so direct-mode .bas files
  like hello.bas, math_ops.bas, string_ops.bas (no line numbers)
  failed with "No program lines found".  load_file now auto-assigns
  line numbers (last_num + 10) to unnumbered lines, with overflow
  protection at line 65520.

- String concatenation in PRINT (codegen.c): emit_str_atom had a
  broken concat loop that emitted "; _cat = gw_str_concat(&...
  _cat.sval ...)" — _cat was never declared, so any program with a
  string-literal concat in PRINT (like PRINT "ABC" + "DEF") failed
  to link.  Concat is properly handled by emit_str_expr's outer
  loop; remove the dead/broken code in the atom.  Fixes
  string_ops.bas.

- Transcendental result type (codegen.c): peek_expr_type returned
  VT_DBL for ATN/LOG/EXP/VAL, so PRINT formatted them with 15-digit
  double precision (e.g. 3.141592653589793) while real GW-BASIC and
  the interpreter format the single-precision result as 3.141593.
  Real GW-BASIC's transcendentals are single-precision; only CDBL
  forces double.  Demote ATN/LOG/EXP/VAL to VT_SNG; CDBL stays
  VT_DBL.  Fixes math_ops.bas.

Also: tests/run_compiler_tests.sh now runs the compiled binary from
the project root rather than the tempdir where it was built, so
test programs that reference tests/programs/ via relative paths
(chain_test, common_test, run_file, misc_stmts) resolve their
targets.  Earlier I'd misdiagnosed those failures as ON ERROR
divergence — they were just CWD-dependent path lookups.

Doc/test counts: 56 → 63 in README, docs/index.md, docs/development.md,
docs/roadmap.md.  Roadmap updated to note the compiler now accepts
unnumbered programs.

docs/development.md

@@ -26,8 +26,8 @@
 
 72 automated test programs in `tests/programs/`, plus 4 classic interactive
 programs in `tests/classic/` (Hamurabi, Lunar Lander, Gunner, Diamond from
-David Ahl's *BASIC Computer Games*).  14 Jupyter kernel tests.  56 compiler
-tests (eligible numbered programs compiled to native executables via
+David Ahl's *BASIC Computer Games*).  14 Jupyter kernel tests.  63 compiler
+tests (eligible programs compiled to native executables via
 `gwbasic-compile`; run `bash tests/run_compiler_tests.sh`).
 
 Run the full automated suite: