Providers as data; add Ollama and Custom endpoints

Every gateway provider is now an entry in providers.json - endpoint and auth
template, how its model list is read, how it is probed before a switch, what
setup asks, which doctor checks apply, and its title, colour and logo -
installed next to the presets and read by all three consumers: the bash CLI
(through cm-json.py), the Windows script, and the bar widget (through
health.json). anthropic stays built in; it is the native login, not a gateway.

Behaviour that differs in kind stays in code, chosen by name from the entry:
catalogue parsers (openrouter, lmstudio, ollama, openai, static), probe rules
(always, lenient, local), and named doctor checks. A provider that reuses them
is an entry and a default preset, with no code. The widget draws providers
from health.json, so a new one needs no QML change and no shell restart.

The existing three are unchanged in behaviour: their blank presets come out
byte-identical from the file, and setup, doctor, models and the picker run the
same checks through the generic paths.

Ollama: local server on :11434, placeholder token, one model for every tier,
models from /api/tags. doctor reads the context each loaded model actually runs
with (/api/ps) and its maximum (/api/show), because Ollama defaults to 4096
tokens unless OLLAMA_CONTEXT_LENGTH is set and silently truncates past it. A
bare model name matches its :latest tag.

Custom: any Anthropic-compatible endpoint. Ships with no address and is refused
until it has one; key optional; models from /v1/models when the endpoint has a
list, and a lenient probe so a proxy without one is not blocked.

Also: preflight (and Set-ClaudeMode on Windows) refuses a preset with no
server address; the server form, setup and set-auth use each provider's own
default URL, key name and placeholder token instead of LM Studio's; the
Windows build gains the no-models and no-address guards it never had.
Tested on Linux against fake Ollama/Custom servers, and on Windows 5.1 in a
USERPROFILE sandbox on winbox.

1.12.0.

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

scripts/build-package.ps1

@@ -33,6 +33,7 @@ Copy-Item (Join-Path $root 'claude-mode.ps1')     $stage -Force
 Copy-Item (Join-Path $root 'install.ps1')         $stage -Force
 Copy-Item (Join-Path $root 'profile-snippet.ps1') $stage -Force
 Copy-Item (Join-Path $root 'VERSION')             $stage -Force
+Copy-Item (Join-Path $root 'providers.json')      $stage -Force
 Get-ChildItem (Join-Path $root 'bin')     -File | ForEach-Object { Copy-Item $_.FullName (Join-Path $stage 'bin')     -Force }
 Get-ChildItem (Join-Path $root 'presets') -File | ForEach-Object { Copy-Item $_.FullName (Join-Path $stage 'presets') -Force }
 
@@ -81,6 +82,7 @@ New-Item -ItemType Directory -Path (Join-Path $posixStage 'presets') -Force | Ou
 Get-ChildItem (Join-Path $root 'linux')   -File | ForEach-Object { Copy-Item $_.FullName (Join-Path $posixStage 'linux')   -Force }
 Get-ChildItem (Join-Path $root 'presets') -File | ForEach-Object { Copy-Item $_.FullName (Join-Path $posixStage 'presets') -Force }
 Copy-Item (Join-Path $root 'VERSION') $posixStage -Force
+Copy-Item (Join-Path $root 'providers.json') $posixStage -Force
 
 # Shell scripts authored on Windows carry CRLF, which makes the kernel reject
 # the "#!/usr/bin/env bash" line. Normalise before packaging.
@@ -92,7 +94,7 @@ Get-ChildItem (Join-Path $posixStage 'linux') -File | ForEach-Object {
 $tarName = "claude-mode-$version-posix.tar.gz"
 $tarPath = Join-Path $outDir $tarName
 if (Test-Path -LiteralPath $tarPath) { Remove-Item -LiteralPath $tarPath -Force }
-& tar.exe -czf $tarPath -C $posixStage 'linux' 'presets' 'VERSION'
+& tar.exe -czf $tarPath -C $posixStage 'linux' 'presets' 'VERSION' 'providers.json'
 if ($LASTEXITCODE -ne 0) { throw 'tar failed - cannot build the POSIX package' }
 
 $shaPosix = (Get-FileHash -LiteralPath $tarPath -Algorithm SHA256).Hash.ToLower()