Add developer summit description and criteria (#802)

* Add develope summit description and criteria

* Incorporate feedback

Author: jarrodmillman

content/summits/developer/_index.md

@@ -2,4 +2,18 @@
 title: "Developer Summits"
 ---
 
-The Developer Summits provide a venue for in-person collaboration on issues that affect the scientific Python ecosystem.
+Scientific Python Developer Summits are focused, in-person, invitation-only gatherings of core developers and maintainers from across the ecosystem.
+These are working meetings---not beginner- or newcomer-oriented events---and they typically do not include talks or tutorials.
+Instead, summits provide a collaborative and self-organized space to address shared technical challenges, strengthen coordination between projects, and support the long-term sustainability of the ecosystem.
+Participants coordinate in advance to identify priorities and plan concrete work, ensuring that in-person time is spent effectively.
+Work at summits often involves improving shared infrastructure (e.g., testing, packaging, documentation), aligning developer practices (e.g., governance, release management, community guides), and developing a collective strategic vision for the future of scientific Python.
+
+For an event to be considered a Developer Summit, it should:
+
+- Convene core developers and maintainers from multiple scientific Python projects.
+- Be participant-driven and self-organized, with priorities defined by attendees.
+- Provide time for substantial collaborative technical work, while also leaving space for higher-level discussions where relevant.
+- Focus on issues with cross-project impact, rather than narrowly scoped tasks that impact only a single package or work that one person could reasonably pursue independently.
+
+The Scientific Python project welcomes and endorses many forms of collaborative events and developer meetings.
+However, to preserve a clear scope and shared understanding, only gatherings that meet the above criteria should be referred to as a **Scientific Python Developer Summit**.