commit-lint: bespoke subject-case rejects proper nouns, fails after squash merge

[0xKT]

Problem

The commitlint config uses a bespoke subject-case: [2, "always", ["lower-case"]]
rule that forces the whole subject to lower-case and rejects proper nouns /
acronyms (EverOS, HTTP, API, WhatsApp).

Since the repo squash-merges and uses the PR title as the squash commit subject,
a title like feat(importer): ... with EverOS HTTP backend passes the pre-merge
PR-title check but fails commit-lint on the squash commit once it lands on main
(push event) -- i.e. "passes the PR, fails after merge".

Concrete occurrence: PR #170's squash commit failed the commit messages job
with subject must be lower-case [subject-case].

Root cause

The always lower-case value deviates from the Conventional Commits standard.
@commitlint/config-conventional uses
subject-case: [2, "never", ["sentence-case", "start-case", "pascal-case", "upper-case"]],
which forbids Title Case / ALL CAPS / Sentence case but allows lower-case
subjects with mid-sentence proper nouns.

Fix

Switch the single subject-case line in commitlint.config.cjs to the standard
value. Deliberately NOT extends: @commitlint/config-conventional, to avoid
pulling in body-max-line-length / footer-max-line-length (100, error), which
would newly reject long PR-description lines on the squash body. All other rules
unchanged.

Out of scope

A separate, pre-existing length inconsistency (PR-title subject length vs the
72-char commit-subject check applied to the squash commit) is not addressed here.