cookfs1.9.0: relocate misplaced pkgIndex library to vendorlib_tcl8/win32-x86_64

src/vendormodules_tcl8 is a tm root - a pkgIndex-style directory there is
invisible to tm handling and nothing referenced this copy (experiment
leftover; added in an early bulk commit). Its designed home is the
platform vendor-library tree: pkgIndex-based, win-x64 dll, Tcl 8 ->
src/vendorlib_tcl8/win32-x86_64/ (reachable via make.tcl's bootstrap
lib paths and the libs build; kit inclusion stays declarative via
src/runtime/vendorlib_vfs.toml - no kit content change from this move).

pages.tcl's comment drift from the old TODO-resolution sweep (283ca03b)
reverted per the vendorlib dont-edit-vendor-code contract - the moved
copy is now byte-identical to the working punk86bawt.vfs payload copy.
Smoke-verified: package require cookfs -> 1.9.0 (dll load, Mount cmd
present) from the new location under native tclsh86t.

(tdbc/sqlite3-1.1.5.tm beside it is NOT misplaced - a namespace subdir
in a tm root is correct tm layout: package tdbc::sqlite3.)

Assisted-by: harness=claude; primary-model=claude-fable-5; api-location=anthropic.com

src/vendorlib_tcl8/win32-x86_64/cookfs1.9.0/pages.tcl

@@ -512,9 +512,7 @@ proc cookfs::tcl::pages::pagewrite {name contents} {
     if {!$c(haschanged)} {
         seek $c(fh) $c(indexoffset) start
     }  else  {
-        # FUTURE: Optimize to avoid seeking in subsequent writes
-        # Consider tracking file position to eliminate redundant seek operations
-        # when writing multiple pages sequentially
+        # TODO: optimize not to seek in subsequent writes
         seek $c(fh) 0 end
     }
     if {[catch {