Split the Windows script into modules; drop the Arkylx Index pieces

claude-mode.ps1 was 2,407 lines. It is now 153: the help block, parameters,
paths, the managed-key list, a loader, and the dispatch. The rest moved,
verbatim, into eleven files under lib/ - providers, output, files, core,
vault, switch, guards, health, catalogue, commands, menu - dot-sourced into
the script's scope in their original order, with the same check as the bash
split that every original line landed in exactly one file. Inside a module
$PSScriptRoot is lib\, so the one path beside the main script
(providers.json) now goes through $script:Here.

install.ps1 ships lib\, clearing old modules first. The Windows suite
parses every module and install.ps1 (36 checks, all green on Windows
PowerShell 5.1); install.ps1 is parsed but never run, since it edits the
real profile and User PATH.

linux/bootstrap.sh and scripts/build-package.ps1 existed only to build and
serve packages for the Arkylx Index. Both installers fetch the repository's
own archive, so a push to master is the release; the two scripts, the dist/
ignore and their mentions in the docs are gone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -1,6 +1,6 @@
-# LF in every working tree, Windows checkouts included. A CRLF shell script
-# fails its #! line, and the packages are built from a Windows checkout
-# (scripts/build-package.ps1 normalises too, as a backstop).
+# LF in every working tree, Windows checkouts included: a CRLF shell script
+# fails its #! line, and a Windows checkout is exactly where the repository's
+# shell scripts would otherwise pick CRLF up.
 * text=auto eol=lf
 
 *.png binary