Store the usage data opt-out as a single global setting

[rhennigan]

Summary

The Share anonymous usage data checkbox in the preferences panel (from #237) stored its state in the front end and re-deployed every configured built-in toolset whenever it was toggled — far too slow for a checkbox. This replaces that with a single machine-wide setting on disk that every built-in server reads when it starts, so toggling it is instant and never touches any client configuration.

• Global settings store (Kernel/Files.wl): $rootPath/GlobalSettings.wxf holds a WXF association read and written by readGlobalSettings, getGlobalSetting, and setGlobalSetting (a missing or unreadable file counts as no settings; writes merge into the existing settings). It currently has one entry, "SubmitUsageData", but is meant to take other global settings later.
• Enabling logic (Kernel/Server/UsageData.wl): getGlobalUsageDataSetting/setGlobalUsageDataSetting wrap that entry (only an explicit False opts out), and usageDataEnabledQ now requires "EnableUsageData" -> True and no global opt-out when SUBMIT_USAGE_DATA is unset. An explicit SUBMIT_USAGE_DATA in a client configuration still wins in both directions, so the "SubmitUsageData" option of InstallMCPServer is unchanged.
• Checkbox (Kernel/PreferencesContent.wl): now a DynamicModule whose Initialization reads the stored value when the panel is displayed and whose Dynamic setter writes it (through catchAlways, so a failed write can't surface as an uncaught Throw in the front end). The usageDataOptOutQ/usageDataDeployOptions/applyUsageDataSetting/redeployForUsageData helpers are gone, and deployments made from the panel no longer pass "SubmitUsageData".
• CreatePreferencesContent wraps its result in UsingFrontEnd: its subtitle is a StringTemplate built from a front-end string resource, so the panel can now be built (and smoke-tested) in a headless kernel without FrontEndObject::notavail.
• Tests: a shared withTemporaryRoot helper in Tests/Common.wl (Blocks $rootPath to a temporary directory); new tests in Files.wlt, UsageData.wlt, and PreferencesContent.wlt.
• Docs: usage-data.md, preferences-content.md, mcp-clients.md, servers.md, Specs/UsageData.md, AGENTS.md.

No migration of the old front-end setting is needed: the previous checkbox never shipped in a tagged release.

Test plan

• Tests/Files.wlt: settings file location; unset ⇒ <||> / Missing / default with nothing created; set/get round trip; merging keeps other keys; unreadable and non-association files count as no settings and are replaced by the next write
• Tests/UsageData.wlt: getGlobalUsageDataSetting default / opt-out / opt-in, other settings preserved, only an explicit False opts out, non-boolean values rejected; usageDataEnabledQ honors the global opt-out, the environment variable still takes precedence, opting back in restores the default; initializeUsageData reads the opt-out at startup (the existing property-dependent tests now run under a temporary root so a developer's own opt-out can't affect them) — 59/59 including the subprocess integration tests
• Tests/PreferencesContent.wlt: checkbox structure (DynamicModule whose Initialization reads the setting), the setter writes the file and updates the module variable, the checkbox contains no deploy/SessionSubmit logic; CreatePreferencesContent-SmokeTest now passes headlessly — 7/7
• Regression: InstallMCPServer.wlt, DeployAgentTools.wlt, MCPServerObject.wlt — 689/689; CodeInspector clean on every changed file
• Preferences panel checkbox in the desktop front end (not verifiable headless here)

🤖 Generated with Claude Code

https://claude.ai/code/session_01MKdo7zY8D9SN5oYaBFvJ4k

[Copilot]

Pull request overview

This PR changes the anonymous usage-data opt-out from a front-end/private setting that triggered slow re-deployments into a single machine-wide on-disk setting ($rootPath/GlobalSettings.wxf) that each built-in server reads at startup, making the preferences checkbox toggle effectively instant and independent of client configuration.

Changes:

• Added a global settings store (readGlobalSettings / getGlobalSetting / setGlobalSetting) backed by $rootPath/GlobalSettings.wxf.
• Updated usage-data enablement to also honor a global opt-out (getGlobalUsageDataSetting / setGlobalUsageDataSetting) when SUBMIT_USAGE_DATA is unset.
• Reworked the preferences checkbox to read/write the global setting via a DynamicModule, removed re-deploy logic, and added/updated tests + docs accordingly.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Kernel/Files.wl	Introduces the machine-wide global settings file and read/get/set helpers.
Kernel/CommonSymbols.wl	Exposes the new global settings / usage-data-setting symbols for cross-file use.
Kernel/Server/UsageData.wl	Adds global-opt-out wrappers and integrates them into usageDataEnabledQ.
Kernel/PreferencesContent.wl	Switches the checkbox to a DynamicModule that reads/writes the global setting; stops passing "SubmitUsageData" into deployments; wraps panel build in UsingFrontEnd.
Tests/Common.wl	Adds withTemporaryRoot to isolate tests from developer-machine settings.
Tests/Files.wlt	Adds coverage for global settings file behavior (missing, read, merge, unreadable, overwrite-on-write).
Tests/UsageData.wlt	Adds tests for global opt-out/in behavior and environment precedence; ensures startup reads global setting.
Tests/PreferencesContent.wlt	Updates tests to validate checkbox structure/setter and absence of redeploy / submit logic.
Specs/UsageData.md	Updates spec to reflect the new global-setting-based opt-out behavior.
docs/usage-data.md	Documents the global settings file and updated opt-out/in semantics and precedence.
docs/preferences-content.md	Updates checkbox documentation and notes UsingFrontEnd behavior for headless kernels.
docs/mcp-clients.md	Clarifies "SubmitUsageData" -> Automatic behavior with global opt-out.
docs/servers.md	Updates server docs to describe global checkbox behavior for built-in servers.
AGENTS.md	Updates repo guidance to mention the global settings store and usage-data opt-out location.

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