docs: link SEP-2640 across repo and tidy Related Work table (#90)

* Update documentation for Skills Extension SEP and related resources

- Revised links and descriptions in README.md to reflect the submitted Skills Extension SEP (PR #2640).
- Updated current status in approaches.md to indicate submission of the Skills Extension SEP.
- Clarified tracking information in open-questions.md regarding the Skills Extension SEP submission.
- Adjusted related work in related-work.md to include the Skills Extension SEP and mark a rejected proposal.
- Changed status in sep-draft-skills-extension.md to 'submitted' and updated author information.
- Enhanced skill-uri-scheme.md to indicate the incorporation of feedback into the submitted Skills Extension SEP.

* Move rejected SEP-2093 to the bottom of SEPs and Proposals table

Keeps the list active-proposals-first so readers aren't distracted by the
struck-out entry.

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Mark SEP-2076 as closed and move to the bottom of proposals table

PR #2076 was closed without merge on 2026-02-24.

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Use SEP-2640 naming convention per MCP SEP guidelines

Per https://modelcontextprotocol.io/community/sep-guidelines, a submitted
SEP is named "SEP-<PR-number>". Rename in-repo references from "PR #2640"
to "SEP-2640" and update the draft doc heading from the "SEP-0000"
placeholder to "SEP-2640".

Also mark Approach 1's SEP-2076 status as closed (2026-02-24, no sponsor
found); approaches.md still listed it as "Draft, seeking sponsor".

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Fix SEP-2076 closure rationale

Closure followed the WG's decision to first explore a convention-based
approach using existing primitives, not a sponsor issue.

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Refine SEP-2640 description in README to clarify proposal details

* Link issues and meeting notes in Open Questions README row

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Surface SEP-2640 in README and related-work table order

README: move the Skills Extension SEP from the bottom of the Repository
Contents table to sit after Approaches, matching the narrative flow
(framing → options → proposal → supporting material).

related-work.md: lead the SEPs and Proposals table with SEP-2640 (this
WG's headline proposal), followed by the prerequisite PR #2527.

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Add 'Open work' link to README header pointing to open PRs

Signals that alternative proposals, decisions, implementations, and
other in-flight contributions are welcome — SEP-2640 is one direction,
not the only one.

🦉 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/approaches.md

@@ -17,7 +17,7 @@ Several design considerations are emerging from community discussion:
 
 The approaches below span a spectrum. At one end, skills become a first-class MCP primitive with dedicated protocol methods (Approach 1). At the other, existing primitives are used with documented conventions (Approach 6). A key question for this WG is whether convention can prove patterns before standardization — or whether the ecosystem needs protocol-level support to achieve reliable interoperability. These are not mutually exclusive; convention work can inform and de-risk a future protocol extension.
 
-**Current status:** The convention approach (Approach 6) was pursued and quickly evolved into a formal Extensions Track SEP ([#69](https://github.com/modelcontextprotocol/experimental-ext-skills/pull/69)), building on convergence across 4+ independent `skill://` implementations. The SEP uses existing Resources primitives with zero protocol changes, positioning it between pure convention and a new primitive. See [#75](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/75) for tracking.
+**Current status:** The convention approach (Approach 6) was pursued and quickly evolved into a formal Extensions Track SEP ([#69](https://github.com/modelcontextprotocol/experimental-ext-skills/pull/69)), building on convergence across 4+ independent `skill://` implementations. The SEP uses existing Resources primitives with zero protocol changes, positioning it between pure convention and a new primitive. See [#75](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/75) for tracking. Submitted to the MCP spec as [SEP-2640](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2640) on 2026-04-23.
 
 ## 1. Skills as Distinct MCP Primitives
 
@@ -35,7 +35,7 @@ Add Agent Skills as a first-class, discoverable primitive in MCP. A skill is a n
 - Progressive disclosure: clients load skill summaries at startup, fetch full instructions on demand
 - Mapping to existing SKILL.md format
 
-**Status:** Draft, seeking sponsor.
+**Status:** Closed on 2026-02-24 after the WG decided to first explore a convention-based approach using existing primitives. See [SEP-2640](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2640) for the resulting Resources-based proposal.
 
 **Community input:**