fix(sequentialthinking): harden thought-box rendering and validation

[1060996408]

Description

Hardens the sequentialthinking reference server against several real-world inputs that currently render incorrectly or are silently ignored, and reports the right package version to MCP clients.

Server Details

• Server: sequentialthinking
• Changes to: tool handler, formatThought rendering, processThought API contract, server version reporting, cross-field input validation

Motivation and Context

While reading through the smallest reference server, the existing test output itself revealed alignment problems in the rendered thought box. Pulling the thread surfaced 11 distinct issues, all in lib.ts / index.ts:

#	Where	Issue
1	formatThought	Header row was missing right-side padding, so when the thought was longer than the header the right │ of the header line hung in mid-air.
2	formatThought	header.length included chalk's ANSI escape bytes, inflating the computed border width.
3	formatThought	Thoughts containing \n broke the box layout (subsequent lines escaped the right border).
4	displayWidth (new)	CJK ideographs were counted as 1 column instead of 2, narrowing the box.
5	displayWidth	SMP-plane emoji (💭 🔄 🌿 — the prefixes the server itself emits) were counted as 1 column.
6	displayWidth	ZWJ-joined emoji like 👨‍💻 were counted as 5 columns instead of 2.
7	formatThought	\t characters were emitted verbatim; terminals advance to the next tab stop and broke the right border.
8	formatThought	A long single-line thought produced a box wider than the terminal.
9	processThought	Auto-adjusting totalThoughts mutated the caller-supplied input object.
10	index.ts	McpServer was constructed with a hardcoded "0.2.0" while package.json had drifted to 0.6.2, so clients saw a stale version in serverInfo.
11	handler	No cross-field validation: isRevision: true without revisesThought silently rendered (revising thought undefined); branchFromThought without branchId silently dropped the branch entry.

How Has This Been Tested?

• npm test in src/sequentialthinking — 46 / 46 passing (was 14 / 14 before)
• npm run build — clean under TypeScript strict mode
• Wire-level smoke test via stdio JSON-RPC: serverInfo.version correctly reports 0.6.2, and tools/call with isRevision: true and no revisesThought returns a well-formed isError response ("revisesThought is required when isRevision is true") instead of rendering (revising thought undefined).
• I have not wired this through a real LLM client end-to-end — happy to do that if a maintainer wants a specific scenario validated.

Coverage gain:

• lib.ts: 84.93 % → 100 % line, 91.35 % branch
• index.ts: 0 % → 80 % line (handler is now extracted and tested)
• all files: ~50 % → 88.88 %

Breaking Changes

None. All changes are backward-compatible:

• Bugs 1–8 fix rendering for inputs that previously produced visibly broken output.
• Bug 9 only changes whether the caller's object is mutated; the response shape and thoughtHistory content are unchanged.
• Bug 10 changes the version string the server reports — from a stale value to the correct one.
• Bug 11 turns inputs that previously silently misrendered into proper isError responses. A client that was relying on the broken behaviour would have been seeing nonsense; the new error message points at the actual problem.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality) — validateThoughtData
• Breaking change
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follow MCP security best practices (no new IO, no new env vars, no new dependencies)
• I have updated the server's README accordingly — README only documents inputs and config, neither of which change in this PR
• I have tested this with an LLM client — wire-level smoke test only, see "How Has This Been Tested?"
• My code follows the repository's style guidelines (kebab-case files, 2-space indent, Zod for input shape, .js import suffix)
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options — none added

Additional context

• All Unicode-width handling is implemented via Node's built-in Intl.Segmenter — no new dependencies.
• The new displayWidth and wrapToWidth are exported from lib.ts so they are independently unit-tested and could be reused by other servers if useful.
• The handler in index.ts is now an exported handleSequentialThinkingTool function. The auto-start of runServer() is guarded by an ESM import.meta.url === pathToFileURL(process.argv[1]).href check so importing the module in tests does not boot the stdio loop.
• The commits are split as:
  1. fix(sequentialthinking): harden thought-box rendering and add cross-field validation — all lib.ts changes
  2. refactor(sequentialthinking): sync server version, extract handler, wire validator — all index.ts changes

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