[content] Resolve concrete step relationship classes

[saskliutas]

Closes #1442

Updated createRelationshipPathJoinInfo to return RelationshipPathStepJoinInfo per step. This info contains selectors for source, target and relationship class ids. They can be used in ECSQL to query concrete classes for particular step.
Updated content source resolved to resolve concreate relationship classes for each step when resolving relationship path.

[changeset-bot]

🦋 Changeset detected

Latest commit: fc252fd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@itwin/presentation-shared	Minor
@itwin/presentation-core-interop	Patch
@itwin/presentation-hierarchies-react	Patch
@itwin/presentation-hierarchies	Patch
@itwin/unified-selection	Patch

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[Copilot]

Pull request overview

This PR addresses iTwin/presentation issue #1442 by ensuring relationship-path resolution yields concrete relationship classes per step (not just concrete entity endpoints), enabling downstream ECSQL consumers to distinguish polymorphic relationship subclasses.

Changes:

• Extended ECSql.createRelationshipPathJoinInfo to return per-step selectors (steps[]) for relationship/source/target ECClassId values.
• Updated content source resolution queries and row-mapping to project/group by concrete relationship classes and write them into ResolvedPath.step.relationshipName.
• Updated/added unit tests, API report, docs, and a changeset for the shared-package API change.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/shared/src/shared/ecsql-snippets/ECSqlJoinSnippets.ts	Adds steps[] to join-info with selectors for concrete relationship/source/target class ids; supports both nav-property and link-table steps.
packages/shared/src/test/ecsql-snippets/ECSqlJoinSnippets.test.ts	Updates tests to assert steps[] and adds coverage for source/target class id selectors.
packages/shared/api/presentation-shared.api.md	Updates extracted public API to include RelationshipPathStepJoinInfo and RelationshipPathJoinInfo.steps.
packages/content/src/content/ResolveContentSources.ts	Projects and groups by relationship class ids per step in resolution queries; maps rows back to concrete relationshipName per step.
packages/content/src/test/Content.test.ts	Updates mocks and expectations to account for relationship-class projection and the new join-info API.
packages/content/src/content/ContentTarget.ts	Clarifies ResolvedPath contract: all step classes (source/target/relationship) are concrete and subclasses produce separate paths.
.changeset/yummy-lands-think.md	Declares a version bump + changelog entry for the public API update in @itwin/presentation-shared.