fix(knowledge): align package entrypoints with mjs build

[CooperSheroy]

Summary

• update MemoryKnowledge package main to the actual dist/server.mjs output emitted by tsdown
• update the tracked knowledge-server and knowledge-mcp CLI wrappers to import the emitted .mjs files

Fixes #783.

Verification

• cd MemoryKnowledge && ./node_modules/.bin/tsdown --config tsdown.config.ts
• node -e 'const p=require("./MemoryKnowledge/package.json"); const fs=require("fs"); for (const f of [p.main, p.bin["knowledge-server"], p.bin["knowledge-mcp"]]) { if (!fs.existsSync("MemoryKnowledge/"+f.replace(/^\\.\\//,""))) throw new Error(f+" missing before build"); } console.log("package entry files exist")'
• git diff --check

Note: cd MemoryKnowledge && ./node_modules/.bin/tsc --noEmit still fails on existing src/middleware/response-envelope.ts(47,9): Type 'Promise<string>' is not assignable to type 'string', which appears tracked separately in #784.