feat(adr): establish a performance working group

docs/adr/performance-wg.md

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+# ADR #306: Performance Working Group
+
+## Status
+
+Proposed
+
+## Submitters
+
+- @wesleytodd
+
+## Decision Owners
+
+- @expressjs/express-tc
+
+## Context
+
+Express has traditionally taken a very lax approach to performance. Historically this has meant poor outcomes with
+and lack of visibility around how changes impact performance. The goal of this working
+group is to centralize discussion so the whole ecosystem of packages can benefit from targeted performance work. The
+scope of this WG would be all active packages in the `expressjs`, `pillarjs` and `jshttp` orgs with an initial focus on
+the ones which are direct dependencies of `express` itself. 
+
+**Why do we need a working group?**
+
+The current state is we have many open PRs, in flight initiatives, and planned future work. With a loose approach we
+can easily have duplicated work, conflicting approaches, or focus on the wrong outcomes. By giving this WG scope over
+this we can centralize the discussion and plans so that we unlock better and faster work in the individual packages.
+
+Additionally, there will be continued long term work to monitor and maintain the tooling. The WG structure gives a clear
+place for users, contributors, and other interested parties to go so it is less difficult to find across the many org's
+and repositories the project owns.
+
+## Decision
+
+Similar to the Security WG, we will setup a new repo (expressjs/perf-wg) and corresponding plan of action. The WG will
+be delegated responsibility for driving concensus on initiatives within scope. This group will have three primary goals:
+
+1. Organize the effort. We want to make sure we are not rebuilding the same things or having the same disucssions in
+   many package repos at once.
+2. Provide and maintain tooling for all the packages/repos to produce reliable performance metrics and benchmarks.
+   Examples include: workflows, infra and guidelines on types of benchmarks
+3. Proritize and execute performance improvements across the packages. These do not need to be done *by* the members of
+   the WG, but it would be good if we could get reviews by the team we will setup to ensure folks with most experience
+   can help address performance issues across the project.
+
+We will need to take a few actions to get this started:
+
+1. Create a new `perf-wg` repo
+2. Create teams: `@expressjs/perf-wg`, `@pillarjs/perf-wg`, `@jshttp/perf-wg`
+3. Write charter/goals doc in the new repo
+4. Schedule a recurring (monthly) meeting
+
+### Relation to STF
+
+Lastly, this kicko-off work is being funded by the STF program. It is a part of our larger work around security
+improvements for the project. There are two parts of that program which fall under this WG's purview:
+
+1. Milestone 6: Monitor performance across Express and direct dependencies
+  - Owner: @wesleytodd
+  - Delivery Date: Dec 31, 2025
+  - Estimated Budget: €25,200
+2. Milestone 9: Improve performance for Express and critical dependencies
+  - Owner: @wesleytodd & @blakeembrey
+  - Delivery Date: Jun 30, 2026
+  - Estimated Budget: €46,200
+
+This funding does not mean the work can only be done by the owners, it just means that we are responsible for organizing
+and executing on the deliverables. This is our first attempt at doing a program like this, so feedback is welcome.
+
+## References
+
+- https://github.com/expressjs/express/pull/6129
+- https://github.com/expressjs/express/issues/5998
+- open-telemetry/opentelemetry-js-contrib#2437
+- openjs-foundation/infrastructure#5