Fix array of tables replacing a dotted key swallowing the next sibling (#542)

[HarperZ9]

Fixes #542.

Assigning an array of tables over a dotted key swallows the following sibling on round-trip:

import tomlkit
doc = tomlkit.parse("a.b = 1\nc.d = 2\n")
aot = tomlkit.aot()
t = tomlkit.table(); t["x"] = 9
aot.append(t)
doc["a"] = aot
print(tomlkit.dumps(doc))

Before:

[[a]]
x = 9
c.d = 2

c.d is captured by [[a]], so it round-trips to {"a": [{"x": 9, "c": {"d": 2}}]} and the top-level c is lost.

Cause

In Container._replace_at, the dotted_to_header guard recognises only non-super Tables, not AoTs. That guard drives the "drop the dotted prefix and move the new header past the inline entries (plain values and dotted keys) it would otherwise capture" path that already fixes the table case (#513 / #524). Because an AoT never matched it, replacing a dotted key with an array of tables left the [[a]] header in the dotted key's inline slot, capturing the next dotted sibling.

Fix

Extend dotted_to_header to also cover AoT (an array of tables always renders with its own [[header]], so it needs the same treatment as a non-super table). One-line logic change.

After:

c.d = 2

[[a]]
x = 9

Round-trips to {"c": {"d": 2}, "a": [{"x": 9}]}.

Adds test_replace_dotted_key_with_aot_keeps_following_sibling (mirrors the existing #513 table test) and a changelog entry. Full suite passes; ruff check / ruff format are clean.