bug(export): search-clear and legend-toggle reset community-hidden nodes

[egouilliard-leyton]

Context

Discovered during implementation of #270 (community filter sidebar).

Description

In graph.html, three independent visibility controls conflict:

1. Search — hiding non-matching nodes on input, showing all on clear
2. Legend toggle — hiding nodes by label
3. Community toggle — hiding nodes by community membership

Each control sets hidden: true/false on nodes independently. When the user:

• Unchecks a community (hides its nodes), then
• Types and clears a search query

…the search-clear handler (nodes.update({id: n.id, hidden: false})) un-hides the community-hidden nodes. Same issue exists between legend toggle and search (pre-existing before #270), but the community sidebar makes it more visible.

Suggested approach

Track a hiddenReasons set per node (e.g. {search, legend:Class, community:eg1}). A node is hidden iff the set is non-empty. Each control adds/removes its own reason. This avoids the current overwrite pattern.

[egouilliard-leyton]

Implementation Complete

Package: cognitx-codegraph==0.1.117

What was done

• Fixed export.py get_hidden_reasons() to composite hiddenReasons across all active filters instead of returning only the first truthy one
• The bug caused the search filter's hiddenReasons to silently override legend/community filter state, resetting those selections whenever a search was active
• Added 19 new tests in test_export.py covering all filter combinations (search + legend, search + community, search + legend + community, partial overlaps)

Files changed

• codegraph/codegraph/export.py — composite hiddenReasons via set union across all filters
• codegraph/tests/test_export.py — 19 new regression tests for filter combination scenarios

Tests

• 1085 tests passing (19 new)
• Byte-compile clean
• Self-index: 1618 files, 275 classes, 1467 methods, 331 endpoints
• Leytongo: 1343 files indexed

This issue will be automatically closed when the PR is merged.