Direct-link + whole-program by default for program runs; open for the REPL

Running a program is a closed world — every namespace is required, then it runs
to completion — so make it direct-link by default (inlining, record shapes, the
inference's specialization), and for a -m/-M entry auto-enable the whole-program
cross-namespace inference pass. A decomposed multi-namespace program was ~3.7x
slower than the same code in one namespace purely because per-namespace
inference can't see a caller in a not-yet-loaded namespace; this closes that for
the common case with no flags and no hints.

Interactive modes (repl, -e, nrepl-server) stay indirect/open — they have to let
you redefine vars, which direct-linking seals against. Opt-outs:
JOLT_NO_DIRECT_LINK forces the open path even for a program run (hot-reload,
runtime redefinition); JOLT_NO_WHOLE_PROGRAM keeps direct-linking but per-ns;
JOLT_DIRECT_LINK / JOLT_WHOLE_PROGRAM still force-on. Namespaces required inside
-main (after the batch pass) fall back to per-ns inference.

The success checker (RFC 0006) rides on the inference for free, but a casual
program run shouldn't spam type warnings just because it now direct-links, so its
default-on is suppressed when direct-linking was auto-enabled (:direct-link-auto?);
an explicit JOLT_DIRECT_LINK or JOLT_TYPE_CHECK still turns it on. whole-program-
test and devirt-test opt their per-ns baseline out of the new auto-default.

Docs: RFC 0005 gains 'Compilation modes and defaults' + 'Cross-namespace
inference'; RFC 0004 documents cross-ns/param hints; self-hosting-compiler and
--help updated. Full gate green.

test/integration/devirt-test.janet

@@ -25,7 +25,9 @@
          "           (mapv area [(->Rect 2 3) (->Circ 2)])))\n"))       # heterogeneous: [6 12]
   (def out (string dir "/out.txt"))
   (def jbin (string (os/cwd) "/" jolt))
-  (def cmd (string (if whole? "JOLT_WHOLE_PROGRAM=1 " "")
+  # -m auto-enables whole-program under direct-linking now, so the per-ns case
+  # (whole? false) must explicitly opt out to test the dispatched/per-ns path.
+  (def cmd (string (if whole? "JOLT_WHOLE_PROGRAM=1 " "JOLT_NO_WHOLE_PROGRAM=1 ")
                    "JOLT_DIRECT_LINK=1 JOLT_PATH=" dir " " jbin " -m dv > " out " 2>&1"))
   (os/execute ["sh" "-c" cmd] :p)
   (string/trimr (slurp out)))