Run wrapped tools directly as vintner <tool> ..., no PATH needed

`vintner cl ...`, `vintner msbuild ...`, etc. now work without adding
<dest>/bin/<arch> to PATH or relying on the same-directory symlinks
`install` sets up there. wrapper.Run gained an explicit binDir
parameter (empty string preserves the existing os.Executable()-based
self-location for the ordinary multi-call/symlink case) so
cmd/vintner's new runTool can point it at a resolved toolchain
directory instead.

Resolution order: VINTNER_BIN if set (same meaning as `env --bin` -
point it at a <dest>/bin/<arch> directory directly, for a non-default
--dest or a specific architecture), else <defaultToolchainDir>/bin/
<hostArch> - the layout a plain `vintner download && vintner install`
with no --dest override produces. A missing toolchain gets a clear
error pointing at both fixes, rather than bubbling up whatever
wineenv.Load's env.json error looks like.

Also fixed shell completion falling out of sync with the actual tool
list: the bash/zsh scripts previously hand-copied tool/flag names
(and had already gone stale once - --with-dxsdk was missing from the
download flag completions since it was added). The tool name list is
now generated from wrapper.ToolNames() instead of hand-maintained,
and both scripts now complete tool names too, so `vintner <TAB>`
suggests `cl`, `link`, `msbuild`, etc. alongside the management
subcommands.

Verified end-to-end with a minimal PATH (/usr/bin:/bin only, no
toolchain dir on it at all): `vintner cl /nologo hello.c` compiled
successfully, and `vintner msbuild -t:Rebuild ...` rebuilt the same
real KMDF driver verified earlier this session - both via the default
~/.vintner/bin/<hostArch> resolution, no VINTNER_BIN override needed.

internal/i18n/i18n.go

@@ -84,7 +84,10 @@ has many, including --with-wdk, --with-dxsdk, --list-workloads,
 Language: set VINTNER_LANG=ru (or LANG=ru_RU...) for Russian output.
 Completion: source <(vintner completion bash)  # or zsh
 
-Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
+Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly,
+or skip PATH and run them through vintner itself - "vintner cl ...",
+"vintner msbuild ...", etc. (set VINTNER_BIN to a <dir>/bin/<arch> if it's
+not the default ~/.vintner/bin/<host-arch>):
   cl, link, lib, ml, ml64, mc, midl, mt, rc, dumpbin, msbuild, nmake, armasm, armasm64, cmd, findstr
 `,
 		RU: `vintner — кросс-компиляция настоящим MSVC на Linux через Wine
@@ -104,9 +107,13 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
 
 --dest/[каталог] по умолчанию — ~/.vintner.
 Язык: установите VINTNER_LANG=en (или LANG=en_US...) для вывода на английском.
+Можно не трогать PATH: "vintner cl ...", "vintner msbuild ..." и т.д. работают
+напрямую (VINTNER_BIN — если каталог не стандартный ~/.vintner/bin/<hostarch>).
 Автодополнение: source <(vintner completion bash)  # или zsh
 
-После установки добавьте <dir>/bin/<arch> в PATH и вызывайте инструменты напрямую:
+После установки добавьте <dir>/bin/<arch> в PATH и вызывайте инструменты
+напрямую, либо не трогая PATH — «vintner cl ...», «vintner msbuild ...»
+и т.д.:
   cl, link, lib, ml, ml64, mc, midl, mt, rc, dumpbin, msbuild, nmake, armasm, armasm64, cmd, findstr
 `,
 	},
@@ -124,8 +131,8 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
 		RU: "Каталог не указан, используется значение по умолчанию: %s",
 	},
 	"install.done": {
-		EN: "Done. Add %s to PATH to use cl, link, lib, ...",
-		RU: "Готово. Добавьте %s в PATH, чтобы использовать cl, link, lib и т.д.",
+		EN: "Done. Add %s to PATH to use cl, link, lib, ... directly, or run them as \"vintner cl\", \"vintner link\", etc. without touching PATH.",
+		RU: "Готово. Добавьте %s в PATH, чтобы использовать cl, link, lib и т.д. напрямую, либо запускайте их как «vintner cl», «vintner link» и т.д., не трогая PATH.",
 	},
 
 	"env.usage": {