Added a blame ignore list for the mechanical header and version passes (#763)

Running git blame on a file header returns a tree-wide copyright, disclosure or
version-constant pass rather than the commit that last touched the code. There
have been 11 such passes in this repository since 2024, and every header line
in the tree now points at one of them.

Added .git-blame-ignore-revs listing those commits. GitHub applies the file to
its blame view automatically; locally it takes one git config command, which
the file documents in its own header.

Additive. No source file is touched, and every listed commit was verified to be
an ancestor of dev.

Assisted-by: Claude Code (Opus 5) <noreply@anthropic.com>

.git-blame-ignore-revs

@@ -0,0 +1,54 @@
+# Commits that changed file headers, copyright lines or version constants across
+# the whole tree. They carry no behavioural change, so `git blame` should look
+# through them to the commit that last touched the code itself.
+#
+# GitHub applies this file automatically. To use it locally, run once:
+#
+#     git config blame.ignoreRevsFile .git-blame-ignore-revs
+#
+# Add a commit here only when it is mechanical and repository-wide. A commit
+# that changes behaviour does not belong in this file, however large it is.
+
+# 2023-10-23  Update release version to 6.3.0 and date to 10-31-2023 (#308)
+# 1366 files
+13b700fd3ed763cedcba7dbd17b859077a01aa9c
+
+# 2024-01-29  Update copyright.
+# 3618 files
+8276bcf71142197e09551e29f1779299fa591ec7
+
+# 2024-01-30  Update version id string.
+# 1048 files
+3e1da1f0b0973e6b833b08b10fb27c7c718835b3
+
+# 2024-02-23  Update the copyright for all assembly files.
+# 798 files
+039a3463974f922f6dd6bfb8afb7ee2895eaebcf
+
+# 2024-02-27  Update version number to 6.4.1
+# 237 files
+27f0ce9ca2334b975c298fd00eac1bc05ecec1f7
+
+# 2025-02-24  Updated ports version to v6.4.2.
+# 235 files
+376e26be292f7d579091650a70b5670195240539
+
+# 2026-03-05  Updated copyright headers and version number constants (#509)
+# 5970 files
+c3259a216026372e3833dd8996a68f77e8595fbd
+
+# 2026-06-03  Release 6.5.1.202602 preparation (#543)
+# 204 files
+de1c6e9bbe13e2db480e4e0ed2d3589ebdd5db27
+
+# 2026-06-06  Added copyright headers to files missing them
+# 581 files
+730b61874bc5cf40768987605ae5187fde0fa1e2
+
+# 2026-06-08  Release 6.5.1.202602a preparation (#547)
+# 207 files
+df30b8b96e4c0c6d72e0bb80d2a2ec31666e5afe
+
+# 2026-09-15  Normalized the AI disclosure comment to one fixed line per file (#740)
+# 455 files
+9e4c57138dfa004cd512b60259c1c5047a8b3dd1