feat(PC0029): trace global variables and cover all record receiver forms

[Arthurvdv]

Why

Issue #515 holds the eight deferred PC0029 ideas. Global variable tracing was approved; the remaining items are closed as won't-do (table below). While testing, three false negatives surfaced: a bare-self key-field write inside a table trigger, a namespaced codeunit with a fully qualified Record variable, and Rec."Primary Key" in the OnRun trigger of a codeunit with TableNo. Fixtures showed that the receiver forms were already handled and that the real gap was the implicit primary key: a table declared without a keys section has a synthesized primary key that ITableTypeSymbol.Keys never lists.

What

• Global variable tracing: when CreateGuid() is assigned to an object-scope Guid variable, the analyzer walks the sibling method and trigger bodies of the same object (text-prefiltered on the variable name) to see whether the value reaches a key field.
• Implicit primary key: key membership now reads ITableTypeSymbol.PrimaryKey before the declared Keys, so tables without a keys section are covered, including tables from referenced apps.
• Parenthesized unwrap: the private one-level UnwrapConversion is replaced by Common's UnwrapConversions(), which also peels IParenthesizedExpression.
• Version gate parity: NoDiagnostic and HasFix call RequireMinimumVersion("16.0") like HasDiagnostic; the AlreadySequentialGuid fixture is back.
• Schema wording: UseSequentialGuidScope now says "field that is part of a table key" instead of "primary key fields".

Receiver-form coverage

26 new fixtures pin every context where Rec or self exists: bare self in table triggers, all self forms in a tableextension, page and pageextension Rec (explicit and bare), request page Rec, report and xmlport Rec via their request page, report dataitem (named and bare), TableNo codeunit OnRun (Rec, bare, Validate), a namespaced file with a fully qualified record type, tables without a keys section, and two NoDiagnostic guards (temporary page source table through Rec; a non-key field of a table without keys). Before the analyzer fix, exactly the five implicit-primary-key cases failed; everything else passed, so no change to GetReceiverTableType was needed.

Guide and follow-ups

• .claude/rules/record-receiver-forms.md is renamed to receiver-forms.md and now documents where each object kind gets its Rec (global vs. the OnRun local vs. none), that bare self binds with a null instance only inside tables and tableextensions, that the four forms apply to fields, record methods and user procedures, the implicit primary key, and namespaces. testing.md, REVIEW.md, the three skills and the regression catalog require the matching fixtures.
• Audit all rules for the four receiver forms on fields and methods, TableNo OnRun Rec, page Rec and namespaces #545 asks for an audit of every rule against these forms and contexts; Audit key-membership logic: ITableTypeSymbol.Keys omits the implicit primary key of tables without a keys section #546 asks for an audit of key-membership logic (and notes that Microsoft's Rule210SuboptimalIndex and Rule222 share the Keys blind spot).

Decision table (from the #515 triage)

Item	Verdict	Reason
RecordRef SetTable() tracing	Won't do	Far too complex for an Info-severity hint
Return value tracing (exit(CreateGuid()), caller assigns to key)	Won't do	Needs a compilation-wide caller scan that re-runs on every editor pass
Global variable tracking	Do	Cheap: the existing symbol tracer already works on any symbol; only the sibling bodies of the same object must be bound
Parameter (var) tracking back to callers	Won't do	Same caller-scan cost as return values
Cross-module opt-in mode	Won't do	Flagging "we cannot see where it goes" is noise
AlreadySequentialGuid NoDiagnostic fixture	Do	Was removed only because the test SDK lacked CreateSequentialGuid(); every PC0029 fixture now runs on runtime 16.0
Suppression attribute/comment	Won't do	#pragma warning disable PC0029 already covers it (documented on alcops.dev)
Event parameter opt-in mode	Won't do	Same category as cross-module

Test notes

• 53 PC0029 test cases pass (42 HasDiagnostic, 9 NoDiagnostic, 2 HasFix); Common tests pass.
• Regression-first: every new HasDiagnostic fixture was committed before the analyzer change it targets and confirmed failing with "no diagnostic at marker".
• All three TFMs compile (netstandard2.1, net8.0, net10.0); dotnet format clean; Validate-Rules.ps1 passes.

Docs companion: ALCops/alcops.dev#184

Closes #515

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