bi-03 step 03 — Spec, source, tests

Goal

Complete the round trip: spec sentence → Blink implementation → the tests that pin it. Then answer the eight gate questions.

Spec. For each case, quote the sentence from the HTML Standard's tree-construction section that causes the observed behaviour. Name the algorithm that relocates a node.
Source. Using spec-phrase search only, locate: the function that performs relocation, the predicate that decides it is needed, the insertion-site locator, and the in-table start-tag handler. Record the query that found each.
The ordering that teaches the design. In the insertion-site locator, note which is checked first — a topmost template or a topmost table. Explain why that order is required.
Tests. Find one C++ unit test, one Blink web test, and one WPT covering this behaviour. Then find where Chromium records a WPT it expects to fail, and note one failing parser-area test as a bi-14 candidate.
The gate. Answer all eight questions for the relocation function in docs/observation.md §8. Question 5 (which thread) has a nuance — the parser directory contains a hint that not all parsing is on one thread.
Complexity notebook. Write entry #1 on insertion modes, and classify the <input type=hidden> rule: principle or fossil? Defend it with CL history.