feat: graduate web-push from experiment to always-on (#24310)

* Removes experiment `web-push`.
* Falls back to NoopWebpusher in case of error
* Checks browser capability in FE
* Adds note to agents getting-started docs regarding webpush without TLS

> 🤖

coderd/apidoc/docs.go

@@ -16176,7 +16176,6 @@ const docTemplate = `{
                 "auto-fill-parameters",
                 "notifications",
                 "workspace-usage",
-                "web-push",
                 "oauth2",
                 "agents",
                 "mcp-server-http",
@@ -16189,7 +16188,6 @@ const docTemplate = `{
                 "ExperimentMCPServerHTTP": "Enables the MCP HTTP server functionality.",
                 "ExperimentNotifications": "Sends notifications via SMTP and webhooks following certain events.",
                 "ExperimentOAuth2": "Enables OAuth2 provider functionality.",
-                "ExperimentWebPush": "Enables web push notifications through the browser.",
                 "ExperimentWorkspaceBuildUpdates": "Enables publishing workspace build updates to the all builds pubsub channel.",
                 "ExperimentWorkspaceUsage": "Enables the new workspace usage tracking."
             },
@@ -16198,7 +16196,6 @@ const docTemplate = `{
                 "This should not be taken out of experiments until we have redesigned the feature.",
                 "Sends notifications via SMTP and webhooks following certain events.",
                 "Enables the new workspace usage tracking.",
-                "Enables web push notifications through the browser.",
                 "Enables OAuth2 provider functionality.",
                 "Enables agent-powered chat functionality.",
                 "Enables the MCP HTTP server functionality.",
@@ -16209,7 +16206,6 @@ const docTemplate = `{
                 "ExperimentAutoFillParameters",
                 "ExperimentNotifications",
                 "ExperimentWorkspaceUsage",
-                "ExperimentWebPush",
                 "ExperimentOAuth2",
                 "ExperimentAgents",
                 "ExperimentMCPServerHTTP",