fix(sequentialthinking): restore nextThoughtNeeded in required schema and dynamic version

[AbhiPra24]

Summary

Fixes #4651 and #4575.

1. Restore nextThoughtNeeded in inputSchema.required (Fixes #4651)

• Problem: nextThoughtNeeded was previously wrapped in a z.preprocess()-based boolean coercion. Zod's toJSONSchema(..., { io: "input" }) treats z.preprocess() input as unknown, silently dropping the field from the emitted required array while runtime validation still requires it, causing -32602 Invalid params for clients constructing calls from the advertised schema.
• Fix: Replaced z.preprocess() with a union transformation:

  const coercedBoolean = z.union([
    z.boolean(),
    z.enum(["true", "false"]).transform((v) => v === "true"),
    z.string().transform((v) => v.toLowerCase() === "true"),
  ]);

  This preserves the input types in the JSON Schema and retains nextThoughtNeeded in required: ["thought", "nextThoughtNeeded", "thoughtNumber", "totalThoughts"].

2. Dynamic Server Version (Fixes #4575)

• Resolves server version dynamically from package.json rather than a hardcoded "0.2.0".

Verification

• Added integration test suite in src/sequentialthinking/__tests__/index.test.ts.
• npm run build and npm test passed (21/21 tests green).

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cc @olaservo for review when available. Thank you!