Add standalone MCP server descriptors to usage data

[rhennigan]

Summary

• Adds two exported symbols, $StandaloneMCPServer and $StandaloneMCPServerInformation, describing the soon-to-be-released standalone MCP server product: a Wolfram kernel that only runs the MCP server, without a full Mathematica installation and under its own licensing. The paclet never sets them (False / <| |>); the standalone application sets both after loading the paclet. They are Protected like the other exported symbols.
• Includes both values in the usage data payload of local server sessions, so sessions of the standalone product can be told apart from those of a regular installation.
• Adds writeRawJSONString and gives it and writeRawJSONFile a shared jsonConvert "ConversionFunction": dates become ISO 8601 strings in UTC and anything else JSON cannot represent becomes its InputForm string. This replaces the level-1 Replace/RuleCondition in $productIdentityInfo, so the session file now stores the kernel's values as they are (None, Infinity) while the JSON sent to the endpoint is unchanged. The JSON body is submitted as UTF-8 bytes rather than a String.
• Updates code comments, docs/usage-data.md (new fields, conversion rules, a "Standalone MCP Server" section), docs/tools.md, Specs/UsageData.md, and AGENTS.md.

Notes for reviewers

• writeRawJSONFile now stringifies values JSON cannot represent instead of failing. The install/uninstall paths in InstallMCPServer.wl still read the written file back and assert equality, so a non-JSON value in a client configuration is still caught.
• The standalone application must set the two symbols after loading the paclet (loading resets them to the defaults) and needs Unprotect or a Block around StartMCPServer, since they are Protected.

Test plan

• Tests/UsageData.wlt (71 tests): new "Standalone MCP Server" section (export, protection, defaults, Block, session-file storage, JSON conversion of nested dates and non-JSON values, invalid values isolated like other tracking failures); updated product identity and JSON payload tests; integration payload of a real server carries the defaults
• Tests/Files.wlt (17 tests): new "JSON Files" section for writeRawJSONString, writeRawJSONFile, and jsonConvert
• Tests/ToolOverrides.wlt (51) and Tests/InstallMCPServer.wlt (487): regression check for the writeRawJSONFile change
• CodeInspector reports no issues on the changed source and test files

🤖 Generated with Claude Code

https://claude.ai/code/session_016kt1pnRU4SjAJZZscqYrGe

[Copilot]

🟡 Changes recommended

The payload validation for $StandaloneMCPServerInformation should enforce the documented “string keys” contract to avoid ambiguous/implicitly stringified JSON keys.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR extends local MCP server usage-data collection to differentiate sessions running under an upcoming standalone MCP server product, and hardens JSON serialization by introducing shared conversion logic for non-JSON Wolfram expressions (including dates).

Changes:

• Adds exported, Protected descriptors $StandaloneMCPServer and $StandaloneMCPServerInformation, and includes them in the local usage-data payload/session file.
• Introduces writeRawJSONString plus a shared jsonConvert conversion function (dates → ISO 8601 UTC; other non-JSON values → InputForm strings) used by both JSON writers.
• Updates tests and documentation/specs to reflect the new payload fields and JSON conversion behavior (including UTF-8 JSON body submission).

File summaries

File	Description
Tests/UsageData.wlt	Expands usage-data tests for standalone descriptors, payload shape, and UTF-8 JSON byte encoding.
Tests/Files.wlt	Adds coverage for writeRawJSONString/writeRawJSONFile and jsonConvert behavior (dates + non-JSON values).
Specs/UsageData.md	Updates usage-data spec with standalone fields and revised JSON conversion rules/body encoding.
PacletInfo.wl	Exports the new standalone descriptor symbols from the paclet.
Kernel/Server/UsageData.wl	Adds standalone fields to usageDataPayload and switches usageDataJSON to UTF-8 ByteArray.
Kernel/Server/Server.wl	Defines default values for $StandaloneMCPServer / $StandaloneMCPServerInformation with product-level documentation.
Kernel/Main.wl	Declares the new exported symbols and adds them to the protected-name list.
Kernel/Files.wl	Implements writeRawJSONString and jsonConvert, and applies jsonConvert as the default JSON conversion function.
Kernel/CommonSymbols.wl	Declares writeRawJSONString in the Common symbols list.
docs/usage-data.md	Documents standalone fields, JSON conversion behavior, and UTF-8 JSON submission details.
docs/tools.md	Notes the standalone descriptors as product-level exported symbols (links to usage-data docs).
AGENTS.md	Updates repository architecture notes to mention the new JSON writer and standalone descriptors.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 1
• Review effort level: Lite

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