Improve clarity and fix typos in need_for_speed lecture

[jstac]

Summary

• Fix typos: "oursives" → "ourselves", stray "for" in heading, missing period, "Python in small" → "Python is small"
• Replace vague "memory slots" with precise "bytes"
• Rewrite parallelization section: swap order to lead with multithreading, add concrete laptop/multi-core example, sharpen the distinction (shared memory vs separate memory spaces), move GIL discussion into a {note}
• Rewrite hardware accelerators section: merge overlapping subsections, explain what a "core" is in a {note}, demote TPUs to a brief mention, streamline single-GPU vs multi-GPU coverage, remove redundant summary

Test plan

• Build the lecture site and verify the page renders correctly
• Check that {note} directives display properly
• Verify figures (geforce.png, dgx.png) still appear

🤖 Generated with Claude Code

[jstac]

What we changed and why

This PR improves the need_for_speed lecture through a combination of typo fixes and substantive rewrites:

Typo fixes:

• "oursives" → "ourselves", "Python in small" → "Python is small", stray "for" in a heading, missing period, vague "memory slots" → "bytes"

Parallelization section rewrite:

• Swapped the order so multithreading comes first — it's what students will encounter in practice (e.g., NumPy splitting work across cores on a laptop)
• Added a concrete example: splitting a large array operation across multiple CPU cores on a single machine
• Sharpened the key distinction: threads share memory (no copying) vs processes have separate memory (must pass data)
• Moved the GIL discussion into a {note} so it doesn't interrupt the main flow
• Replaced the generic "Advantages and Disadvantages" section with a focused "Which Should We Use?" section

Hardware accelerators rewrite:

• Merged the overlapping "GPUs and TPUs" and "Why TPUs/GPUs Matter" subsections into a single clear narrative
• Added a {note} explaining what a "core" actually is — the word was used without definition, and it means very different things for CPUs vs GPUs
• Demoted TPUs to a brief mention (they were given equal billing but then disappeared from the rest of the section)
• Consolidated the "Single GPU" / "Multi-GPU" / "Summary" subsections into one tighter "Accessing GPU Resources" section, removing repeated mentions of JAX and "later lectures"

[github-actions]

🚀 Deployed on https://69db767d3fe211d7bf18118d--epic-agnesi-957267.netlify.app

[mmcky]

✅ Translation sync completed (zh-cn)

Target repo: QuantEcon/lecture-python-programming.zh-cn
Translation PR: QuantEcon/lecture-python-programming.zh-cn#50
Files synced (1):

• lectures/need_for_speed.md

[mmcky]

✅ Translation sync completed (fa)

Target repo: QuantEcon/lecture-python-programming.fa
Translation PR: QuantEcon/lecture-python-programming.fa#97
Files synced (1):

• lectures/need_for_speed.md