Symptom

gog docs write --replace --markdown --tab=<id> does not honour CommonMark / GFM strikethrough syntax (~~text~~). The two tilde pairs and the inner text render as plain literal text instead of producing struck-through formatting (Docs API textStyle.strikethrough = true).

Strikethrough is part of GitHub-Flavored Markdown, which gog's markdown converter otherwise supports (**bold**, *italic*, fenced code blocks, tables, etc. all render correctly via the same path).

Repro

echo -e '# Strike test\n\n~~struck out~~ vs **bold** vs *italic*\n' > /tmp/strike.md
DOC=$(gog docs create "strike test" --pageless --file /tmp/strike.md -j | jq -r .id)
gog docs tabs add "$DOC" --title "Tab 2"
TAB=$(gog docs list-tabs "$DOC" -j | jq -r '.tabs[1].id')

# Push the same markdown via the --tab path:
gog docs write "$DOC" --replace --markdown --tab="$TAB" --file /tmp/strike.md

# Verify in the rendered tab:
gog docs read "$DOC" --tab="$TAB"
# Observed:  ~~struck out~~ vs bold vs italic    (tildes survive as literal text)
# Expected:  struck out vs bold vs italic        (struck out should be struck through)

# Confirm in the raw structure — no strikethrough textStyle landed:
gog docs raw "$DOC" -j | jq '.body.content[].paragraph?.elements[]?.textRun?.textStyle?.strikethrough? // empty'
# Observed: no occurrences.

Expected behaviour

~~text~~ from the input markdown should produce a textRun span with textStyle.strikethrough = true in the resulting Doc body — mirroring how **bold** produces textStyle.bold = true today.

Acceptance criteria

• ~~text~~ in the input markdown produces a textRun with textStyle.strikethrough = true for the inner text on both the gog docs write --replace --markdown --tab=<id> (per-tab) and gog docs write --replace --markdown (whole-doc Drive-import) paths.
• The tilde markers are not preserved as visible characters in the rendered doc.
• An --no-strikethrough opt-out is not needed; this should match the other GFM inline styles which require no opt-in.

References

• Docs API TextStyle.strikethrough: https://developers.google.com/workspace/docs/api/reference/rest/v1/documents#TextStyle
• CommonMark + GFM strikethrough extension: https://github.github.com/gfm/#strikethrough-extension-
• Adjacent same-converter bugs on --tab path: docs write --replace --markdown --tab: paragraph blank lines collapse into soft line breaks #644 (closed; paragraph blank-line collapse), bug(docs write --tab): markdown path drops nested-list nesting (children render as plain text) #696 (nested-list nesting drops), perf(docs write --tab --markdown): table cells inserted one-per-batchUpdate; multi-table docs trip Docs API write quota #699 + PR perf(docs write --tab --markdown): batch table-cell inserts into single batchUpdate (fixes #699) #701 (per-cell batchUpdate burst).