feat(link): 連結一律寫成 [文字](絕對網址)，寫入前先驗證連得到

取消 [[頁名]] 與 [[顯示文字|頁名]] 兩種同 wiki 寫法，不再分「同存取庫」與
「跨存取庫」兩條規則。那種寫法只在自己那個 wiki 內解析，寫錯不報錯，畫面上
看起來像普通文字或死連結，巡不到也修不了。

連結寫進頁面前先過 jsc-gitea 的 link-check.sh，結束碼 0 才寫。驗證一律走 API，
不看網頁狀態碼：私有存取庫的網頁網址對未登入請求一律回 404，拿狀態碼判會把
好連結判成壞的。認證失敗回 7，與死連結的 1 分開，免得金鑰一過期就把還在的頁
整批判死。

skills/doctor/SKILL.md

@@ -125,7 +125,23 @@ The script reads the page back, replaces this machine's row or appends it, then
 
 The key is the bare hash and not the link cell for a reason: a cell holding a URL changes whenever `GITEA_HOST` changes, whenever `JSC_WIKI_REPO_CHECK` moves to another repo, or whenever Gitea encodes the page name differently. The comparison then never matches, and every run appends another row for the same machine — silently, because the page still looks right.
 
-Column 1 stays the human-facing link and is never the key. Build it as an **absolute URL** from `gitea.sh wiki-url {CHECK repo} CHECK_{HASH}`. `[[CHECK_{HASH}]]` resolves only inside its own wiki, and the two pages are no longer in the same one. Fetch the URL after `CHECK_{HASH}` is written: `wiki-url` exits 4 on a page that does not exist yet.
+Column 1 stays the human-facing link and is never the key. Write it as `[CHECK_{HASH}]({absolute URL})` — text plus link, the one link form this skill set uses. The URL comes from `gitea.sh wiki-url {CHECK repo} CHECK_{HASH}` and is never composed by hand. Fetch it after `CHECK_{HASH}` is written: `wiki-url` exits 4 on a page that does not exist yet.
+
+A same-wiki link form resolves only inside its own wiki, and the two pages are no longer in the same one. It fails without an error, reading on screen as plain text or a dead link, so nobody finds it and nobody fixes it.
+
+**Verify every link before writing it.** Collect every URL heading into `CHECK_{HASH}` or into the `CHECK_CONTENTS` row, then hand the whole list to `jsc-gitea/tools/link-check.sh`. It prints `{OK|DEAD|SKIP}<TAB>{URL}<TAB>{reason}` per line. Only exit 0 may be written.
+
+| Exit | Meaning | Action |
+| --- | --- | --- |
+| 0 | Every link answers | Write the page |
+| 1 | At least one link is unreachable | Write nothing, on either page. Report the `DEAD` lines to the caller |
+| 2 | Usage error: no URL was given | Report it as a defect in this skill and pass the URLs |
+| 3 | The list holds a Gitea URL but `GITEA_HOST` is unset | Skip both writes and put `GITEA_HOST` at the top of 待修項目. Never write without verifying |
+| 7 | Gitea authentication failed | Stop and report the key problem. This is not a dead link |
+
+Exit 7 stays apart from exit 1 on purpose: with a dead key, Gitea's answer for a private repo looks the same as "page absent". Merge the two and one expired key marks every live page dead, and the rows pointing at them get rewritten or dropped.
+
+The script asks the API and never reads a web status code. A private repo's web URL answers 404 to a request with no credentials, so status codes turn good links into dead ones.
 
 | Exit | Meaning | Action |
 | --- | --- | --- |
@@ -145,4 +161,4 @@ Exits 7 and 8 never mean the page is missing. Writing a fresh template over a di
 
 State the four counts from 2.2's `summary` line: required items missing, settings invalid, CLIs unwired, domains behind. Recommend `/jsc-cli:setup` when any of those is above zero. Never fix anything here.
 
-Done when each of the two pages is reported with its URL, or its skipped write is reported together with its reason, **and** the four counts are stated with the recommendation given or explicitly withheld.
+Done when every link written into either page passed `link-check.sh` first — or the `DEAD` list is on screen and that write was skipped — each of the two pages is reported with its URL, or its skipped write is reported together with its reason, **and** the four counts are stated with the recommendation given or explicitly withheld.