Update docs to reflect convention-to-SEP evolution; link to charter (#78)

docs/approaches.md

@@ -17,6 +17,8 @@ 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 IG 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.
+
 ## 1. Skills as Distinct MCP Primitives
 
 Add Agent Skills as a first-class, discoverable primitive in MCP. A skill is a named bundle of instructions plus references to tools, prompts, and resources that together teach an agent how to perform a domain-specific workflow.
@@ -60,6 +62,7 @@ Examples:
 - Expose skills via tools like `list_skills` and `read_skills`. Server instructions can direct the agent to call the skill tool first.
 - Expose skills as resources (e.g. skill://...), which can also be exposed through tools
 
+**See also:** [#41](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/41) — Server-side reference implementation, [#55](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/55) — Recommended _meta keys for skill resources
 
 **Implementations:** 
 
@@ -97,6 +100,8 @@ Several design considerations have been suggested in community discussion and pr
 - **Git-based distribution:** Versioned distribution via git (tags, pinned refs) can be viable without a formal registry. Clare Liguori (AWS) noted that Terraform operated without a formal registry for a long time — Feb 26 office hours.
 - **Domain-level discovery:** The [Agent Skills Discovery RFC](https://github.com/cloudflare/agent-skills-discovery-rfc) proposes `/.well-known/skills/` for organizations to publish skills at predictable URLs with content integrity (SHA-256 digests). This is complementary to MCP — it handles discovery and distribution while MCP handles runtime consumption.
 
+**See also:** [#44](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/44) — Define well-known URI schemes and naming patterns for skill resources
+
 **Community input:**
 
 > "Installless/temporary/ephemeral skill availability while server is installed feels like a good pattern. Clients could optionally offer to permanently install." — [Sam Morrow](https://github.com/SamMorrowDrums) (GitHub), via Discord
@@ -113,6 +118,8 @@ Instead of exposing skill tools to the main agent, use MCP's Sampling with Tools
 
 **Source:** [jbnitorum](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2076#issuecomment-3806151745)
 
+**See also:** [#42](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/42) — Test skills-via-sampling approach
+
 ## 4. Gateway/Composition Pattern
 
 A gateway-style server that provides a group of MCPs as one, ensuring they get requisite configuration and instructions to work in harmony.
@@ -131,6 +138,8 @@ Use server instructions as a pointer to a resource: "If you need to do X, fetch
 
 ## 6. Official Convention as Intermediate Step
 
+> **Status:** This approach was pursued and graduated into the draft [Skills Extension SEP](https://github.com/modelcontextprotocol/experimental-ext-skills/pull/69) ([#75](https://github.com/modelcontextprotocol/experimental-ext-skills/issues/75)). The SEP formalizes the convention as an Extensions Track specification using existing Resources primitives — zero protocol changes, backward compatible. Content format is delegated to [agentskills.io](https://agentskills.io/specification). The text below is preserved as historical context for how this approach was originally framed.
+
 A documented "MCP Skills Convention" as a middle path between ad-hoc experiments and protocol extension. This could:
 
 - Define well-known URI schemes or naming patterns (e.g., resources matching `**/SKILL.md`). See [Skill URI Scheme Proposal](skill-uri-scheme.md) for a detailed survey and recommendation.
@@ -139,7 +148,7 @@ A documented "MCP Skills Convention" as a middle path between ad-hoc experiments
 - Be documented in MCP docs as a "Pattern" — not in protocol schema, but officially recommended
 - Allow data gathering on adoption before considering protocol-level changes
 
-This mirrors how other ecosystems (e.g., Kubernetes) graduate patterns: start as convention, prove value, then formalize. Could be a concrete IG deliverable: "MCP Skills Convention v0.1."
+This mirrors how other ecosystems (e.g., Kubernetes) graduate patterns: start as convention, prove value, then formalize.
 
 **Advantages of the convention approach:**