Finish remaining C# 9 diagnostics

[BillWagner]

Fixes #53549

New file for command line and build config issues consolidates several existing error codes and takes more off the undocumented backlog.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/language-reference/compiler-messages/attribute-usage-errors.md	Resolve errors and warnings related to attribute declarations or attribute use in your code
docs/csharp/language-reference/compiler-messages/constructor-errors.md	Resolve errors and warnings for constructor declarations and module initializers
docs/csharp/language-reference/compiler-messages/index.md	"Compiler messages"
docs/csharp/language-reference/compiler-messages/invalid-build-command-line.md	Resolve errors and warnings for invalid command-line options and build configuration
docs/csharp/language-reference/compiler-messages/overloaded-operator-errors.md	Resolve errors and warnings for operator declarations and overflow
docs/csharp/language-reference/toc.yml	docs/csharp/language-reference/toc
docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md	Coming in C# 15

[Copilot]

Pull request overview

This PR finishes documenting remaining C# 9 diagnostics by moving several previously “catchall/undocumented” build and command-line-related error codes into a new consolidated article, updating topic pages for the remaining C# 9 diagnostics, and wiring up TOC and redirects for removed per-code pages.

Changes:

• Add invalid-build-command-line.md to document build/command-line/configuration diagnostics (including CS8751, CS8771, and CS8772) in one place.
• Move C# 9 diagnostics to the appropriate existing topic pages (constructor, operator overloads, and attributes), and remove them from the “sorry we don’t have specifics” catchall.
• Remove several old per-code pages and add redirects + TOC updates to keep links working.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md	Removes newly documented diagnostics from the catchall keyword list (but introduces a duplicate keyword entry).
docs/csharp/misc/cs3013.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs3012.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs2036.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs2029.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs2019.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs2008.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs1719.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/misc/cs1668.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/toc.yml	Adds the new consolidated article to the compiler messages TOC and removes direct entries for deleted pages.
docs/csharp/language-reference/compiler-messages/overloaded-operator-errors.md	Adds CS8761 coverage and keywords to the operator diagnostics topic.
docs/csharp/language-reference/compiler-messages/invalid-build-command-line.md	New consolidated diagnostics article (contains a broken relative link and a couple of clarity/typo issues).
docs/csharp/language-reference/compiler-messages/index.md	Updates metadata date for the compiler messages index page.
docs/csharp/language-reference/compiler-messages/cs2032.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/cs1616.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/cs1564.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/cs0016.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/cs0007.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/cs0006.md	Deletes per-code page in favor of consolidated guidance.
docs/csharp/language-reference/compiler-messages/constructor-errors.md	Adds CS8760 coverage and keywords to the constructor diagnostics topic.
docs/csharp/language-reference/compiler-messages/attribute-usage-errors.md	Adds CS8783 coverage and keywords to the attribute diagnostics topic.
.openpublishing.redirection.csharp.json	Adds redirects from removed per-code pages to the new consolidated article.

Comments suppressed due to low confidence (1)

docs/csharp/language-reference/compiler-messages/invalid-build-command-line.md:121

• The CS1773 entry repeats "Invalid version version..." in the section list. If the compiler message doesn't include the repeated word, fix the typo here as well so both lists match.

- **CS1773**: *Invalid version version for /subsystemversion. The version must be 6.02 or greater for ARM or AppContainerExe, and 4.00 or greater otherwise*
- **CS2019**: *Invalid target type for /target: must specify 'exe', 'winexe', 'library', or 'module'*
- **CS2029**: *Invalid name for a preprocessing symbol; 'identifier' is not a valid identifier*