feat(http): enforce static CLI flags as upper bound for per-request filtering

[SamMorrowDrums]

Summary

The HTTP server now respects the same static CLI flags as the stdio server: --toolsets, --tools, --exclude-tools, --read-only, --dynamic-toolsets, and --insiders.

A static inventory is built once at startup from these flags, producing a pre-filtered tool/resource/prompt universe. Per-request headers (X-MCP-Toolsets, X-MCP-Tools, etc.) can only narrow within these bounds, never expand beyond them. When no static flags are set, existing behavior is preserved — headers have full access to all toolsets.

Problem

Users deploying the HTTP server expected --read-only, --toolsets, and other CLI flags to work the same as in stdio mode. Instead, these flags were ignored entirely — any request header could access any tool regardless of server configuration.

Approach

Layer	What it does
Static inventory (startup)	Built once from CLI flags. Pre-filters tools/resources/prompts to create the allowed universe.
Per-request builder (each request)	Starts from the static universe. Headers can narrow (e.g., select a toolset subset) but cannot expand.
Graceful degradation	If a request header asks for a tool not in the static universe, it's silently dropped rather than returning an error.

Key design decisions

• Static tools as upper bound: SetTools(staticTools) means per-request builders physically cannot see tools outside the static set
• Backward compatible: No static flags → full tool universe (existing HTTP behavior unchanged)
• Per-request defaults: When static flags are set, per-request builder defaults to WithToolsets(["all"]) within the static bounds, so all statically-allowed tools are visible unless headers narrow further
• No exported API changes: New fields added to ServerConfig; DefaultInventoryFactory now uses the previously-ignored *ServerConfig parameter

Changes

• pkg/http/server.go — Added ReadOnly, EnabledToolsets, EnabledTools, DynamicToolsets, ExcludeTools, InsidersMode to ServerConfig
• pkg/http/handler.go — buildStaticInventory() pre-filters at startup; DefaultInventoryFactory captures static tools in closure; filterRequestTools() gracefully drops unknown tool names from request headers
• cmd/github-mcp-server/main.go — Wired CLI flags to HTTP ServerConfig (matching stdio pattern)
• pkg/http/handler_test.go — 13 new test cases covering static enforcement, non-overridability, narrowing, combinations, and backward compat

Relevant issues

• Fixes --read-only flag fails to restrict write tools when using the new http command #2156 — --read-only flag fails to restrict write tools in HTTP mode
• Supersedes fix(http): make --read-only flag work in HTTP mode #2200 — which proposed a middleware-only fix for read-only
• Related to Inventory: return stable hidden-tool reason codes across filter gates #2197 — inventory reason codes for hidden tools
• Related to Add read-only regression coverage for dynamic toolsets and deprecated aliases #2192 — read-only regression coverage

Testing

$ script/lint   → 0 issues
$ script/test   → all packages pass

[Copilot]

Pull request overview

This PR fixes #2156 by wiring the static CLI flags (--read-only, --toolsets, --tools, --exclude-tools, --dynamic-toolsets, --insiders) into the HTTP server, ensuring they act as an upper bound on per-request header-based filtering.

Changes:

• Added static filtering fields to ServerConfig and wired CLI flags in main.go
• Built a startup-time static inventory in DefaultInventoryFactory that constrains per-request tool visibility
• Added 13 table-driven tests covering static enforcement, non-overridability, narrowing, and backward compatibility

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
pkg/http/server.go	Added 6 new fields to ServerConfig for static filtering; enhanced startup log
pkg/http/handler.go	Implemented buildStaticInventory, hasStaticConfig, filterRequestTools; updated DefaultInventoryFactory to use static bounds
cmd/github-mcp-server/main.go	Wired CLI flags to HTTP ServerConfig matching stdio pattern
pkg/http/handler_test.go	Added mockToolFull helper and TestStaticConfigEnforcement with 13 test cases

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