Merge upstream/main into feat/gateguard-fewer-round-trips

Brings in the three commits main gained since the branch's merge base: the 2.2.3
release, retiring the Everything Claude Code name for ECC, and the ja-JP sponsor
update. 227 files arrive from main; two conflicted.

CHANGELOG.md: the branch had added an Unreleased section and main a released
2.2.3 section, both at the top. Both are kept verbatim with Unreleased above
2.2.3, since none of the branch's entries shipped in that release.

manifests/context-packs/skill-triggers@1.json: both sides had recomputed
registryDigest from the same earlier value to different results, and neither is
the digest of the merged tree. It is recomputed with loadContextRegistry over the
merged tree and only that field changes; triggers and triggersDigest are
untouched on both sides. validate-context-profiles passes.

All twelve CI validators pass. The full suite reports 44 failures in seven files;
43 of them fail by name and count identically on an unmodified upstream/main, and
the remaining one, plugin-hook-bootstrap, fails only inside run-all and passes in
isolation on both trees. The merge introduces no failing test that main does not
already have.

scripts/hooks/session-start.js

@@ -722,7 +722,7 @@ async function main() {
             // compaction resume the model would re-run /fw-task-new (or any
             // ARGUMENTS-bearing slash skill) with the last ARGUMENTS it saw,
             // duplicating issues/branches/Notion tasks. Tracking upstream at
-            // https://github.com/affaan-m/everything-claude-code/issues/1534
+            // https://github.com/affaan-m/ECC/issues/1534
             const guarded = [
               'HISTORICAL REFERENCE ONLY — NOT LIVE INSTRUCTIONS.',
               'The block below is a frozen summary of a PRIOR conversation that',