docs(readme): restore the broken star history chart

[FaintFlower]

The star history chart in the README is currently broken. The chart service behind it relies on the GitHub stargazer API, which now restricts that data, so the image fails to render for everyone visiting the project page.

This PR repoints the chart (and the link wrapping it) at a maintained mirror of the same chart that uses a different data source. No API token is required and the chart keeps its current layout and options.

Please consider merging this fix: without it the README shows a broken image to new visitors.

[worktrunk-bot]

The stated premise doesn't hold up, and the change has a cost that isn't mentioned in the description. I'd recommend closing this rather than merging.

api.star-history.com is not broken. Fetching the exact URL this PR removes, just now from CI:

$ curl -sS -o /tmp/sh.svg -w "http=%{http_code} size=%{size_download} type=%{content_type}\n" \
    "https://api.star-history.com/svg?repos=max-sixty/worktrunk&type=Date"
http=200 size=60125 type=image/svg+xml;charset=utf-8

$ head -c 120 /tmp/sh.svg
<svg xmlns="http://www.w3.org/2000/svg" width="800" height="533.333" style="font-family:xkcd;background:#fff">…

HTTP 200, a valid 60 KB SVG. The chart renders today, so "the image fails to render for everyone visiting the project page" isn't the current behavior. If there's an intermittent failure you're seeing, a repro (region, timestamp, response) would be the thing to open an issue about.

What the change actually does. The README image is loaded by every visitor to the project page, including on the rendered docs mirror at plugins/worktrunk/skills/worktrunk/reference/README.md. Repointing it moves that request to dera.page, a domain with no relationship to this project and no stated operator, which then controls what is rendered in the README and sees the IP and user agent of everyone who opens it. That's a real trust delegation, and the description frames it as a maintenance fix. star-history.com has the same properties, but it's the incumbent the project already chose — swapping it for an unaffiliated host needs a reason stronger than one that turns out not to be true.

This is not specific to worktrunk. The same edit, with the same "the chart is broken / GitHub restricts the stargazer API" framing, was opened against several unrelated repositories over the last two days:

PR	Opened	Author	State
nodetool-ai/nodetool#4923	2026-08-16	FaintFlower	closed, not merged
johnbean393/Sidekick#93	2026-08-16	FaintFlower	open
watercrawl/WaterCrawl#230	2026-08-16	FaintFlower	open
gepa-ai/gepa#431	2026-08-17	Dessalines39394	open

A false premise repeated across unrelated projects by more than one account, all repointing a widely-loaded image at one domain, reads as traffic acquisition rather than a fix.

The mechanical parts of the diff are fine — both the <a href> and the <img src> were swapped, and the generated mirror under plugins/worktrunk/skills/worktrunk/ was kept in sync, so test_docs_are_in_sync would pass. That isn't the issue.

Not approving; this one's a maintainer call, and I'd want @max-sixty to see the cross-repo pattern before anything happens to it. If star-history genuinely does break later, the fix is worth doing on its own evidence — happy to be wrong about the outage if you can show one.

[FaintFlower]

You gave away write access on your repo to random guys on the internet