PR #524 - bompus/codegraph

The next upstream merge no longer brings back changelog entries the fork removed or reworded, and eight doubled entries are gone from [Unreleased].

Problem

scripts/changelog-reconcile.mjs added every entry in upstream's [Unreleased] that the fork's did not have. An entry the fork had removed or reworded came back on each upstream merge, so each reconcile needed a manual override. Run against the current fork and upstream baf19067, it would re-add four such entries (VB.NET type lookup, CRLF store export, the C++ std::unique_ptr call, the C++ string-literal declaration).
Eight "codegraph sync and the file watcher …" entries appeared twice in [Unreleased] > Fixes. Upstream's own changelog already had both copies at the 5da4a41d reconcile (#499); upstream has since removed its copies, so the fork's second copies were left over.

Change

The script now skips an upstream entry that the merge base's [Unreleased] already had and the fork lacks, and prints it as left out. An entry new since the merge base is still added, and with no merge base nothing is skipped.
The second copy of the eight doubled entries is removed. After this, [Unreleased] has no repeated entry and equals the script's rebuild against upstream/main.
codegraph-build-validation notes the left out line.

Checks

On head fad31b0a:

Check	Result
New test in `fork-tooling-scripts.test.ts` (dropped entry stays out, new one is added, no base re-adds)	fails on the old script, passes here
`fork-tooling-scripts`, `readme-sync`, `prepare-release`	49 passed, 0 failed
`check:agent-docs`	exit 0
Script against `HEAD` and `upstream/main` before the change	would add 4 entries; after: adds 0, lists 4 as left out

README rows checked

None: no user-visible behavior, number or README table changes.

Not covered

An upstream entry the fork never carried because a union merge lost it (not removed on purpose) also stays out; the left out list is where to spot that.

Summary by cubic

The changelog reconcile script no longer re-adds upstream entries the fork removed or reworded, and the eight doubled codegraph sync and the file watcher entries are gone from [Unreleased].

An upstream [Unreleased] entry that the merge base's [Unreleased] already had and the fork lacks is now skipped and reported as left out, instead of coming back on every upstream merge and needing a manual override. Entries new since the merge base are still added; with no merge base, nothing is skipped.