docs: document the x86-64-v2 CPU requirement

[Iheanacho-ai]

What

Documents Talos's x86-64-v2 CPU microarchitecture requirement across all 8 live versions (v1.7–v1.14): added to System Requirements, restored on the Proxmox kvm64 workaround (v1.11–v1.14, where it had been dropped), and linked from the GOAMD64 build option in Building Custom Talos Images.

Why

Closes #725. Talos halts at boot below x86-64-v2 with no matching page to land on and no explanation for the existing kvm64/GOAMD64 workarounds — readers hit the wall with no way to search their way out.

Change

• System Requirements: new "CPU architecture (requirements)" section with the verbatim boot error text, linking to the Proxmox fix and the GOAMD64 option.
• Proxmox (v1.11–v1.14): restored the "why" next to the kvm64 table row and workaround.
• Building Custom Talos Images: GOAMD64=v1 now links back to the requirement it works around.

Testing

• Ran: make broken-links, make validate-docs-nav, make style-check-changed STYLE_CHECK_BASE=upstream/main, make docs.json && git diff --exit-code
• Where: local checkout
• By: agent (Claude)
• Result: all four pass — 0 new style errors/warnings on touched lines, no broken links, nav and docs.json unchanged/current
• Filled from outside the page: none

[sterlingkoch]

Read this while it's still in draft, so just notes rather than a review. The substance holds up well.

The version claim checks out on every page you touched. I verified against upstream rather than the release notes alone: GOAMD64 ?= v2 first appears in the v1.1.0 Makefile (v1.0.0 has no GOAMD64 line at all) and is still v2 at every tag from v1.7.0 through v1.14.0. MinimumGOAMD64Level = 2 confirms the level is v2 and not v3, and in v1.14 that constant moved to build-tagged files (constants/amd64.go at level 2 by default, constants/amd64_v1.go at level 1 under //go:build amd64.v1), which independently confirms GOAMD64=v1 really is the documented escape hatch.

The boot error text is byte-identical to the source, and the v1.7 floor is exactly right. The three strings live in internal/app/init/main.go in cpuInfo(), identical in v1.7.0 and v1.14.0, and the [talos] [initramfs] prefix comes from kmsg.SetupLogger. The check itself arrived in siderolabs/talos#8537, milestone v1.7, and is absent from v1.6.0. So starting the quoted error at v1.7 is correct.

All 28 added links resolve. I checked each one mechanically: target file exists in the same version tree, and for anchored links the heading exists in that file and slugifies to the anchor. Zero failures, no cross-version leakage. The two anchor spellings correctly track the two heading spellings, which is the seven-of-eight bug I was looking for and didn't find.

The heading is fine. ## CPU architecture on v1.7 to v1.11 and ## CPU architecture requirements on v1.12 to v1.14 correctly tracks the sentence-case rewrite those newer pages already had (Minimum requirements, Storage requirements). No existing heading was renamed, so no anchor broke.

Two nits for when you mark it ready:

1. Em dash in the new prose at public/talos/v1.14/getting-started/system-requirements.mdx:90, and the equivalent line in the other seven (v1.7 :84, v1.8 to v1.11 :86, v1.12 and v1.13 :90). House style is a period instead.
2. don't at building-images.mdx:53 against do not in the System Requirements paragraph. Pick one.

Also worth noting the kvm64 explanation is technically right rather than merely plausible: the flag list already on the page (+cx16,+lahf_lm,+popcnt,+sse3,+ssse3,+sse4.1,+sse4.2) is the x86-64-v2 feature set, so "predates the level Talos requires, add these flags" is the correct causal story.

One thing that is out of scope here, filing separately: As of Talos v1.0 is wrong on the v1.6 through v1.10 Proxmox pages (proxmox.mdx:121, and :93 on v1.6). It should be v1.1.0. Those five files aren't in this diff.

[smira]

this applies to amd64 only, arm64 is not covered here