Multi-day accumulated fixes: tag dispatch, session/pooling correctness, SPA rollout, jetc compiler

JetCore engine (Tag.cpp/.h, Global.cpp/.h, __*.cpp tag classes):
- Numerous __mysql.cpp connection-pooling correctness fixes (stale
  result sets, double-indirection sessionid bugs, field caching,
  pool keying) and a session-registration-before-connection-confirmed
  ordering fix (dangling pointer on a failed connect)
- Tag.cpp: large body of fixes to the tag-dispatch/container-scanning
  logic (bare-name fallback, database aliasing, single-quote handling,
  @-prefix session variable resolution, TAGDEF caching, nested split-tag
  scanning for if/while/until/ifrow so an inner one doesn't corrupt an
  outer one's own boundary scan) plus the process-first rendering
  order fix (a <process> now runs before <checksession>/page
  resolution, fixing a real "blank page after successful login" bug)
- Global.h/.cpp: added imapSessions (parallel to the existing __mysql*
  session map) for the new <imap> tag family
- __whiledir.cpp/__include.cpp: caching and directory-name-aliasing
  fixes
- __call.cpp/.h: fixed a dangling-pointer bug
- __write.cpp: fixed an O_WRONLY-only open that couldn't create a new
  file
- __ifrow.cpp/__sql.cpp: fixed the same sessionid double-indirection
  bug __mysql.cpp had (resolveKeyword's result was being used as a map
  key lookup instead of the resolved value itself)

jetc compiler (jetc/JetParser.cpp/.h, JetCodegen.cpp/.h, JetAST.h,
jetc.cpp, build-shared.sh, build-compiled.sh):
- Parser fixes: inline <include>, nested-quote handling, void-tag
  recognition
- Codegen fixes and expanded AST support
- build-shared.sh: atomic rename into place for a freshly-built .jtc
  (a live server dlopen()ing the same path mid-rebuild was corrupting
  its own already-mapped view of the old file) and a staleness check
  so a cached JetCore .o doesn't silently keep serving yesterday's
  fixes forever
- Added -lssl to both build scripts' link lines (needed once the new
  <imap> tag's client-side TLS code existed - previously nothing in
  this codebase used OpenSSL's SSL/TLS client API, only libcrypto)

Site content (jetc/barant-site/): SPA (fetch-and-swap navigation)
rollout across essentially every .page/.jet/.section/.tag/.proc/.method
file - dynamic-content fixes, fragment-mode stripping, native
$[@name] session variables replacing older mechanisms, and this
session's own checkout.page redesign, login start-param redirect fix,
and per-page side-menu (menu.bar/$[PAGE].menu) refresh support.
Completed the earlier main.css/control.css move from assets/ to
assets/images/ (git still showed the old paths as tracked-but-deleted
until now).

Deliberately left out of this commit: dozens of .pre-<description>-
<date> manual backup files (this session's and earlier ones' own
before/after snapshots, not meant for permanent history), compiled
.jtc build outputs, ad hoc test binaries and scripts under jetc/
(login_asan, wcwc_test, optest2_bin, etc.), and jetc/__pycache__/ -
none of these are meant to be tracked; a .gitignore covering them
would be worth adding separately.

jetc/JetCodegen.h

@@ -62,11 +62,28 @@ namespace jetc {
 
     private:
       std::ostringstream out;
+
+      // Free functions generated for compiled <tag name="X"> definitions
+      // (see the TAGDEF case in emitNode) accumulate here, in the order
+      // encountered, and are spliced into the final output ahead of the
+      // entry function (see generate()) - C++ doesn't care about
+      // definition order within one translation unit as long as nothing
+      // outside of it needs a forward declaration, but keeping them
+      // grouped together ahead of the entry point makes the generated
+      // file easier to read/debug than interleaving them positionally.
+      std::ostringstream tagDefFuncs;
+
       size_t nextId = 0;
       std::string id(const std::string &prefix) { return prefix + std::to_string(nextId++) + "_"; }
 
-      void emitBody(const std::vector<NodePtr> &nodes, int indent);
-      void emitNode(const NodePtr &n, int indent);
+      // target is the stream this node's statements are written to - `out`
+      // for everything at the top level or nested inside ordinary control
+      // flow (IF/FOR/WHILE bodies stay in the same stream as their
+      // enclosing scope), but a TAGDEF's own body is rendered into a
+      // fresh stream to become a separate generated function (see
+      // emitNode's TAGDEF case) rather than being inlined in place.
+      void emitBody(const std::vector<NodePtr> &nodes, int indent, std::ostringstream &target);
+      void emitNode(const NodePtr &n, int indent, std::ostringstream &target);
       static std::string ind(int indent);
       static std::string cstr(const std::string &raw);   // C++ string-literal escape
       static const char *staticTypeOp(const std::string &type, const char *rcVar);