all: fix duplicate package docs and tighten TestPackageDocsmain

TestPackageDocs walked into directories starting with "." (such as
.claude worktrees) and only logged warnings on duplicate package docs
across files in a directory. Skip dot-directories (which covers the
old .git but also .claude), ignore files with "//go:build ignore" so
command files don't falsely trip the duplicate check, and promote the
duplicate-doc warning to a t.Errorf.

While here, deduplicate the package docs that were previously only
logged: drop the redundant comment from client/systray/startup-creator.go,
move the comprehensive taildrop doc into feature/taildrop/doc.go, and
remove a leftover doc fragment from feature/condlite/expvar/omit.go.

The tstest/integration/vms allowlist is no longer needed since the
//go:build ignore filter now handles its dns_tester.go and udp_tester.go
files generically.

Fixes #19526

Change-Id: Id794d96bd728826a1883a054e4a244f90fa05d3d
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

0 files changed, 0 insertions, 0 deletions