feat: add ErrorContextAnalyser for sliding-window error/warning surfacing

Walks Entry[] once and emits one ErrorContextProblem per ERROR or
WARNING entry, attaching up to 20 entries before and 20 after as
context. Overlapping windows clip the second hit's before- and
after-ranges so no Entry appears in two context arrays. Caps emission
at 500 hits and adds an ErrorContextTruncatedInformation when reached.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Analysis/ProjectZomboid/ErrorContextProblem.php

@@ -0,0 +1,130 @@
+<?php
+
+namespace IndifferentKetchup\Codex\Analysis\ProjectZomboid;
+
+use IndifferentKetchup\Codex\Analysis\InsightInterface;
+use IndifferentKetchup\Codex\Analysis\Problem;
+use IndifferentKetchup\Codex\Log\EntryInterface;
+
+/**
+ * Problem emitted by ErrorContextAnalyser for each ERROR or WARNING entry,
+ * carrying a sliding window of surrounding entries as before/after
+ * context. Coalesced by 1-based entryIndex so re-adding the same hit
+ * never produces duplicate problems.
+ */
+class ErrorContextProblem extends Problem
+{
+    private string $type = 'error';
+    private int $entryIndex = 0;
+
+    /**
+     * @var EntryInterface[]
+     */
+    private array $before = [];
+
+    /**
+     * @var EntryInterface[]
+     */
+    private array $after = [];
+
+    /**
+     * @param string $type 'error' or 'warning'
+     * @return $this
+     */
+    public function setType(string $type): static
+    {
+        $this->type = $type;
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getType(): string
+    {
+        return $this->type;
+    }
+
+    /**
+     * @param int $entryIndex 1-based index of the hit entry within the log
+     * @return $this
+     */
+    public function setEntryIndex(int $entryIndex): static
+    {
+        $this->entryIndex = $entryIndex;
+        return $this;
+    }
+
+    /**
+     * @return int 1-based index of the hit entry within the log
+     */
+    public function getEntryIndex(): int
+    {
+        return $this->entryIndex;
+    }
+
+    /**
+     * @param EntryInterface[] $entries
+     * @return $this
+     */
+    public function setBefore(array $entries): static
+    {
+        $this->before = $entries;
+        return $this;
+    }
+
+    /**
+     * @return EntryInterface[]
+     */
+    public function getBefore(): array
+    {
+        return $this->before;
+    }
+
+    /**
+     * @param EntryInterface[] $entries
+     * @return $this
+     */
+    public function setAfter(array $entries): static
+    {
+        $this->after = $entries;
+        return $this;
+    }
+
+    /**
+     * @return EntryInterface[]
+     */
+    public function getAfter(): array
+    {
+        return $this->after;
+    }
+
+    /**
+     * Convenience accessor returning before-context, hit entry, and
+     * after-context as a single ordered array of at most
+     * ErrorContextAnalyser::CONTEXT_BEFORE + 1 + CONTEXT_AFTER = 41
+     * entries.
+     *
+     * @return EntryInterface[]
+     */
+    public function getContext(): array
+    {
+        return [...$this->before, $this->getEntry(), ...$this->after];
+    }
+
+    public function getMessage(): string
+    {
+        return sprintf(
+            '%s at entry %d (%d before, %d after)',
+            strtoupper($this->type),
+            $this->entryIndex,
+            count($this->before),
+            count($this->after)
+        );
+    }
+
+    public function isEqual(InsightInterface $insight): bool
+    {
+        return $insight instanceof self && $insight->getEntryIndex() === $this->entryIndex;
+    }
+}