fix(tooling): marker-guard false-positive across tags — carry marker state across diff hunks

[anandgupta42]

Found during v0.8.1 release review (Tech Lead, P2). parseDiffForMarkerWarnings (script/upstream/analyze.ts:~754) resets inMarkerBlock=false at every hunk boundary, so when an enclosing altimate_change start marker lives in an earlier hunk that doesn't reappear as context (e.g. --base v0.8.0), correctly-marked code is false-flagged. CI uses --base main which passes, but cross-tag audits mis-report. Seed inMarkerBlock from a full-file marker scan, or use a large -U context.