sequentialthinking: thought log formatting prints "undefined" and draws the box too wide

[cliffhall]

Problem

The formatted thought log written to stderr has three defects:

• A revision with no revisesThought prints "revising thought undefined".
• A branchFromThought with no branchId draws a Branch header reading "ID: undefined".
• The border width counts the header's colour escape codes, so the box is drawn wider than its text.

Where it is pinned

src/sequentialthinking/__tests__/thought-logging.test.ts: "prints 'undefined' for a revision with no revisesThought", "draws a branch header even when no branch is recorded (no branchId)", "sizes the border from the coloured header, escape codes included", added in #4970 (Wave 1 of #4857). Each of these tests carries a KNOWN BUG marker: it asserts the current, wrong behavior, so the fix has to change it.

Expected

No "undefined" in headers, and the border is sized from the visible text.

Done when

• The behavior above is fixed, in the legacy-era (2025-11-25) server on SDK 1.x.
• The pinning tests assert the correct behavior, and their KNOWN BUG markers are gone.
• The per-file 90% coverage gate still passes.

[cliffhall]

Fixed by #5031, merged to v2/main (Wave 4 of #5004). The combined wave was proven in rollup #5044, which had green CI.