feat: match repeated findings across scan history (#575)

* feat: preserve finding relationships in scan history

* feat: match repeated findings across scans

* refactor: reuse indexed finding relationships

* refactor: walk unread finding pages once

* fix: read omitted findings before finishing comparisons

* fix: recompute complete finding comparisons

* fix: validate and isolate scan matching

* fix: keep matcher declarations independent of SDK internals

* fix: preserve confirmed finding relationships during matching

* fix: preserve related findings throughout comparison workflows

* fix: preserve finding identities across plugin protocol versions

* fix: preserve transitive confirmed finding identities

* fix: preserve comparison identities and discover protocol support

* fix: canonicalize confirmed identities and wrapped capabilities

* fix: support maximum reasoning effort in finding matching

* test: align history fixtures with confirmed identities

* fix: include stable finding identities in linked history

* fix: keep matcher environment helper out of public types

* fix: forward API keys to finding matching

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Co-authored-by: mldangelo-oai <269034524+mldangelo-oai@users.noreply.github.com>