docs: repair application-specific release installation recipes

[joshrotenberg]

Scope

Fixes #1183. Leaves #1087 open.

Two documentation files only:

• Select explicit redisctl-v0.12.1 / redisctl-mcp-v0.12.1 release assets and explain why repository-wide latest is ambiguous.
• Extract cargo-dist's top-level directory into a temporary directory before installing the CLI.
• Replace the nonexistent Linux ARM64 native archive recipe with Cargo/container alternatives.
• Update illustrative version output and the Windows/MCP archive PATH instructions.

No release/publish actions, runtime changes, supported-target changes, credential/onboarding policy decisions, repository settings, or database migration default cutover. Existing scoped PRs #1182, #1180 and #1178 remain untouched.

Validation

• All 8 documented release/asset URLs returned HTTP 200; all 6 download assets were also present in their application-specific published release.
• Checksum-verified published Apple ARM64 CLI archive: top-level layout confirmed; binary reports redisctl 0.12.1.
• Executed the Apple Silicon code block extracted from the changed Markdown, substituting ONLY the privileged installation destination with a disposable local bin directory. Download/extraction/install/version all passed. No remote installer scripts executed and no customer config or credentials used.
• Strict MkDocs passed (final wording: 1.40 s); git diff --check, formatting and cargo clippy --all-targets --all-features -- -D warnings passed before final push.
• Whole-file Markdown lint remains nonzero, with exactly the same 20 baseline diagnostics: CLI MD046 x9 + MD040 x1; MCP MD031 x4 + MD046 x6. No rules disabled beyond the existing CI arguments and no new lint diagnostics introduced. Tabbed MkDocs formatting predates this change.
• Final two-file diff self-review found no further actionable issue. Independent read-only agent review at the exact pushed head also found no actionable findings; it verified the scoped acceptance, release metadata, GNU/BSD tar compatibility and retained smoke evidence. It did not execute other-platform recipes/remote installers or inspect other archive layouts.
• Linux/Intel/Windows installation execution, Docker and full workspace/integration suites were not run locally for this documentation-only change; exact-head hosted CI is now complete.

Checkpoint

Head: 19376e6e70813a3a4e348b7151d7859026fe4748.
Implementation, local documentation/artifact validation, independent review and exact-head CI are finished. 15 checks passed with 7 expected skips (PR release/publishing/deployment and coverage). Verified underlying required steps: formatting/Clippy, all three unit suites, integration/live opt-in pilot/command-safety tests, Linux workspace tests, Linux/macOS/Windows builds, strict MkDocs and default/all-feature Rustdoc. Hosted advisory lint does not erase the 20 unchanged local baseline diagnostics above.

CI, Documentation, Release plan all completed successfully at this head. Ready for required human review; Josh's merge decision remains separate. No merge or release.