feat(dispatch): file-name routing via auto-renamed Main symbols (AOT)

Lets app/api/foo.prg keep its idiomatic `FUNCTION Main()` shape while
multiple such files compile into one binary. fnode auto-renames each
library file's Main into a unique symbol derived from the basename:

  app/api/hello.prg       -> HELLO__MAIN
  app/api/admin-stats.prg -> ADMIN_STATS__MAIN  (hyphen -> underscore)

Three moving parts:

  cmd/fnode/main.go
    parseOne for every PRG, then rename Main on every file except
    the first (the entry). crossFile map updated so the analyzer
    treats the renamed symbol as declared.

  hbrtl_ext/dispatch/dispatch.go
    New HB_FUNC FNODE_CALL(cFuncName) that does VM.FindSymbol +
    PushSymbol/Function dance and discards the return value. Same
    pattern pgserver's callPRG helper uses internally.

  app/bridge_server.prg
    BridgeDispatch now derives the symbol name from hReq["path"]
    ( /api/foo[.prg] -> FOO__MAIN ), invokes FNODE_CALL, and
    maps "not found" errors to HTTP 404 (other errors -> 500).
    Hardcoded /api/hello and /api/echo handlers replaced by the
    path-driven model.

Verified end-to-end with app/api/hello.prg and app/api/admin-stats.prg:
  GET /api/hello.prg                  -> 200 + JSON from HELLO__MAIN
  GET /api/hello                      -> 200 (extension optional)
  GET /api/admin-stats.prg?from=2026  -> 200 from ADMIN_STATS__MAIN
                                          with query string echoed
  GET /api/nope                       -> 404 "function not found"

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

hbrtl_ext/dispatch/dispatch.go

@@ -0,0 +1,42 @@
+// Package dispatch exposes one helper for PRG code: a dynamic
+// "call this function by name" hook that pairs with fnode's auto-
+// renamed Main symbols. Lets the bridge dispatcher route an HTTP
+// path to the right Main without needing a hard-coded `DO CASE`.
+//
+// PRG surface
+//
+//	cErr := FNODE_CALL(cFuncName)  -> "" on success, error text on failure
+//
+// The called function runs on the same Thread; output is left in the
+// bridge_capi per-thread output buffer (use _OUT_GET to read it).
+// Return values from the called function are discarded — call the
+// generated symbol directly when you need its return value.
+package dispatch
+
+import (
+	"strings"
+
+	"five/hbrt"
+)
+
+func init() {
+	hbrt.HB_FUNC("FNODE_CALL", fnodeCall)
+}
+
+func fnodeCall(ctx *hbrt.HBContext) {
+	if ctx.PCount() < 1 || !ctx.IsChar(1) {
+		ctx.RetC("FNODE_CALL: function name required")
+		return
+	}
+	name := strings.ToUpper(ctx.ParC(1))
+	sym := ctx.T.VM().FindSymbol(name)
+	if sym == nil {
+		ctx.RetC("function not found: " + ctx.ParC(1))
+		return
+	}
+	ctx.T.PushSymbol(sym)
+	ctx.T.PushNil() // self placeholder
+	ctx.T.Function(0)
+	_ = ctx.T.Pop2() // discard return value
+	ctx.RetC("")
+}