Add links and a version timeline to the Go brief

.agents/skills/quiz/SKILL.md

@@ -34,7 +34,7 @@ Quiz the user on one or more topic briefs in `docs/topics/`, one question at a t
 1. Ask one question, prefixed with its progress and source: `**Q3/10** (golang — Concurrency)`. Base it on the concept: ask about its key fact, number, or gotcha — not "explain <heading>". Don't include hints or the answer.
 2. Stop and wait for the user's answer. Never ask the next question in the same message.
 3. Grade the answer against the concept's bullets:
-   - **Correct** — covers the concept's core point (usually the bold terms). Wording and minor omissions don't matter.
+   - **Correct** — covers the concept's core point (its key fact, number, or gotcha). Wording and minor omissions don't matter.
    - **Incorrect** — wrong, missing the core point, "skip", or "I don't know".
    State the verdict, then give the concept's key points in 1–3 sentences, naming anything the user missed or got wrong.
 4. Ask the next question in the same message as the verdict, so the user only has to type answers.

AGENTS.md

@@ -7,6 +7,7 @@ This repo is a set of concise topic briefs for technical interview prep. The rea
 - `docs/topics/` — one brief per topic (e.g. `docs/topics/golang.md`).
 - `docs/index.md` — the reading site's homepage.
 - `scripts/lint_briefs.py` — checks the format rules below; CI runs it with the strict site build on every pull request.
+- `scripts/check_links.py` — fetches every external link in the given briefs (default: all) and checks it resolves and its `#anchor` exists. Not in CI because it depends on the network; run it after adding or changing links.
 - `.agents/skills/quiz/` — the `quiz` skill, which quizzes the user on brief concepts. `.claude/skills/quiz` is a symlink to it so Claude Code and Codex share one copy.
 - File names are lowercase, single word or kebab-case.
 - `README.md` and `docs/index.md` list every topic with a link and a one-line summary, and `zensical.toml` lists it in the site nav. Update all three when adding or renaming a file.
@@ -25,31 +26,33 @@ What experienced Go engineers forget before an interview, grouped by subtopic.
 
 ### Scheduler (GMP)
 
-- Goroutines (G) run on OS threads (M) through logical processors (P); **`GOMAXPROCS`** = number of Ps.
-- `GOMAXPROCS` respects the container CPU limit **since Go 1.25**; before that it used the host CPU count.
-- Blocking syscall → the M is parked and the P moves to another M; network I/O goes through the **netpoller** and doesn't hold a thread.
-- Preemption is asynchronous (signal-based) **since Go 1.14**, so tight loops no longer starve the scheduler.
+- Goroutines (G) run on OS threads (M) through logical processors (P); `GOMAXPROCS` = number of Ps.
+- `GOMAXPROCS` respects the container CPU limit since Go 1.25; before that it used the host CPU count.
+- Blocking syscall → the M is parked and the P moves to another M; network I/O goes through the netpoller and doesn't hold a thread.
+- Preemption is asynchronous (signal-based) since Go 1.14, so tight loops no longer starve the scheduler.
 
 ### Channel axioms
 
 | Operation | nil channel | closed channel |
 |---|---|---|
-| send | blocks forever | **panics** |
+| send | blocks forever | panics |
 | receive | blocks forever | zero value, `ok == false` |
-| close | panics | **panics** |
+| close | panics | panics |
 ```
 
 ### Rules
 
 - **Title**: `# <Topic>` (e.g. `# Go`, `# Distributed Systems`). No "Cheatsheet" suffix.
 - **Intro**: one line: "What experienced <topic> engineers forget before an interview, grouped by subtopic." Adjust wording for non-language topics (e.g. "Key system design building blocks and trade-offs, grouped by subtopic.").
-- **`##` = subtopic** (Concurrency, Memory management, …). Named, not numbered. Ordered by how often the area comes up in interviews. At least 2 concepts each; fold a lone concept into a related subtopic.
+- **`##` = subtopic** (Concurrency, Memory management, …). Named, not numbered. Ordered by how often the area comes up in interviews; the only exception is a `## Timeline`, which goes first. At least 2 concepts each; fold a lone concept into a related subtopic.
 - **`###` = concept** — a noun phrase (`### Scheduler (GMP)`, `### Isolation anomalies`), never a question, no numbers. Each concept should be self-contained (no "as above"): the quiz picks `###` headings at random.
 - **Body of a concept**: 2–6 bullets, or one short paragraph, or one compact table. One fact per bullet, one line where possible.
 - **Tables** for comparisons and matrices (channel axioms, isolation levels vs anomalies, deployment strategies, promise combinators).
 - **Code** only when shorter than prose; ≤ 6 lines.
-- **Bold** the term or number worth memorizing — at most 3 per concept, not counting tables.
+- **No bold** in briefs, tables included. Format identifiers, flags, commands, and file names as code; let the wording carry emphasis.
 - **Versions**: note when behavior changed ("since Go 1.22", "Python 3.14+", "Pectra, May 2025").
+- **Timeline** (optional, for language and tool briefs): a `## Timeline` section with two concepts, `### Language and runtime changes` and `### Library and tooling changes`, each a `Version | Key changes` table, oldest first. Link each version to its release notes and each change to the section that describes it. List only changes an interviewer could ask about.
+- **External links**: link terms a reader may want to look up. Prefer official sources (language spec, reference manuals, API docs such as pkg.go.dev, release notes, the project's blog); use Wikipedia or another well-known reference for general CS terms. Link a term's first mention in each concept, since concepts are read in isolation, and never link inside headings. Percent-encode parentheses in URLs (`%28`, `%29`). Run `python scripts/check_links.py <brief>` before finishing.
 - **Cross-topic**: the owner file covers a concept in full; another file may overlap briefly from its own angle and links to the owner: `see [security.md](security.md)` (rules in Topic ownership). Link to files, not anchors (the strict build validates anchors; only use one if you've checked the slug).
 - Suggested size: 5–20 sections, 3–8 concepts each. Shorter is better if nothing is lost.
 
@@ -99,6 +102,5 @@ Each concept has one owner file that covers it in full. Other files may overlap
 ## Style
 
 - Concise and accurate over exhaustive. Cut anything that doesn't help recall.
-- Use **bold** for the one or two terms worth memorizing in each answer.
 - No filler, no marketing tone, no emojis.
 - Verify facts against current language/tool versions; note the version when behavior changed (e.g. "since Go 1.22").

docs/javascripts/external-links.js

@@ -0,0 +1,9 @@
+// Open external links in page content in a new tab; site links stay in the current tab.
+document$.subscribe(() => {
+  for (const link of document.querySelectorAll(".md-content a[href]")) {
+    if (link.hostname && link.hostname !== location.hostname) {
+      link.target = "_blank";
+      link.rel = "noopener";
+    }
+  }
+});