docs: add Copilot instructions modeled on plugin_evidence

[TheWitness]

Adds/aligns .github/copilot-instructions.md to follow the structure used in Cacti/plugin_evidence, tailored to this plugin's actual hooks, database tables, naming conventions, and security-sensitive areas.

[Copilot]

🟡 Changes recommended

The guide contains unresolved omissions and inaccurate implementation guidance that should be corrected before approval.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds repository-specific Copilot instructions for the Cacti Intropage plugin.

Changes:

• Documents project structure, conventions, architecture, and compatibility.
• Adds database, security, localization, hook, and panel guidance.
• Provides common pitfalls and repository references.

File summaries

File	Description
.github/copilot-instructions.md	Adds tailored Copilot development instructions for the Intropage plugin.

Review details

Suppressed comments (5)

.github/copilot-instructions.md:55

• The table inventory is incomplete. include/database.php creates plugin_intropage_panel_dashboard, plugin_intropage_trends, plugin_intropage_dashboard, and plugin_intropage_user_group_auth as well; omitting them can lead contributors to miss real dashboard, trend, and group-authorization storage.

Plugin tables are prefixed `plugin_intropage_`: `plugin_intropage_panel_definition`, `plugin_intropage_user_auth`, `plugin_intropage_panel_data`.

.github/copilot-instructions.md:92

• This access-control guidance omits the registered administration realm. setup.php registers both intropage.php and intropage_admin.php, and administrative code checks the latter; documenting only the viewer check can cause new administration paths to use incomplete realm protection.

Realm permissions: `api_user_realm_auth('intropage.php')` gates access. Panel permissions: `is_panel_allowed()` checks user/group authorization before rendering a panel.

.github/copilot-instructions.md:120

• This hook list is not the actual set registered by setup.php; it omits config_arrays, login_options_navigate, top_graph_header_tabs, graph_buttons_thumbnails, the user action/save hooks, the group action/save hooks, and user_admin_setup_sql_save. Contributors following this as the plugin's hook guidance could omit required integration points.

Register hooks in `setup.php`: `config_settings`, `top_header_tabs`, `console_after`, `page_head`, `graph_buttons`, `poller_bottom`, `user_admin_tab`, plus the user/group admin lifecycle hooks (`user_remove`, `user_group_admin_tab`, `user_group_remove`, `copy_user`).

.github/copilot-instructions.md:115

• The data-flow statement says all user permissions live in plugin_intropage_user_auth, but group permissions are stored separately in plugin_intropage_user_group_auth and merged by is_panel_allowed(). This omission is especially misleading because the same guide documents group-admin hooks.

3. User permissions live in `plugin_intropage_user_auth` (JSON-encoded).

.github/copilot-instructions.md:110

• panellib/index.php is matched by the documented glob but is an entry point rather than a panel library; initialize_panel_library() explicitly skips it (include/functions.php:1179). Qualify this requirement so contributors do not add a nonexistent register_index() function.

Every panel library file (`panellib/*.php`) MUST define a `register_<basename>()` function returning a panels array with keys like `name`, `description`, `class`, `level` (`PANEL_SYSTEM`/`PANEL_USER`), `refresh`, `width`, `height`, `priority`, `alarm`, `requires`, `update_func`, `details_func`, `trends_func`.

• Files reviewed: 1/1 changed files
• Comments generated: 4
• Review effort level: Lite

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[bmfmancini]

LGTM