Analyzers README promises an Error never reports more within a major; 2.3.0's CMTK0003 does, with no decision record #153

Found by a pre-release sweep of release/2.3.0 @ 99c6032 (weaving-review §8, "Analyzer Errors freeze"); read from the source and the analyzer's own tests.

Problem

The Analyzers README promises consumers that an Error rule never widens inside a major version:

Within a major version, an Error never reports more than it did. A new Error rule, or an Error that reports more, waits for the next major version.

(src/CodoMetis.TypeKit.Analyzers/README.md:759-760, and decision 34.)

2.3.0 widens CMTK0003, which is an Error since 2.0.0. It now also reports an assertion of CodoMetis.TypeKit.Testing on a Task or ValueTask that is left without await (IgnoredOutcomeAnalyzer.cs:157-159, IsPendingAssertion). The changelog announces it ("an assertion left without await is reported (CMTK0003)"), and IgnoredOutcomeAnalyzerTests.cs:120-123 holds it:

{|#1:service.FindAsync().ShouldBeNone()|};   // CMTK0003, Error, new in 2.3.0

Nothing records the exception:

• No decision after 0034 allows it.
• The CMTK0003 row in design/analyzers.md:36 doesn't list the form.
• The README sentence stays as it is, so the shipped 2.3.0 README contradicts the shipped 2.3.0 analyzer.

The exception is sound in substance. Every such assertion is new in 2.3, so no build that worked on 2.2.0 breaks, as the code comment says. What's missing is the written decision. #152 widens the same form further before the tag, and the same decision covers it.

Change

• A decision record: an Error may report, in a minor version, a form that only an API new in that version can write, because it breaks no build that worked before. Add its row to design/adr/README.md.
• The README's "What a new version may change" sentence states that exception.
• The CMTK0003 row of design/analyzers.md lists the dropped pending assertion.
• Then decide whether CMTK0003 misses dropped async assertions through Task wrappers and branches #152's wider reach ships in 2.3.0, under the same rule: the forms freeze at the tag.

Test

The README sentence becomes a claim in test/oracles/claims.json, quoted verbatim, so OracleCatalogueTests notices when it is reworded. It is held by the test that pins CMTK0003's severity, or waived with a reason.