docs: Plugin system documentation and discoverability (#203)

[deucebucket]

Summary

• Added Python drop-in plugin guide (manifest.json schema, BasePlugin interface, quick start steps) directly in the Plugins settings tab sidebar
• Added secrets management card explaining secrets.json usage for both Docker and bare metal
• Added ready-to-use API configurations for Google Books and Open Library with exact JSONPath mappings
• Shipped example-logger plugin to examples/plugins/ with comprehensive README
• Added new hint entries for plugin-related tooltips

Test plan

• Open Settings > Integrations tab, scroll through the Plugins sidebar cards
• Verify Python Drop-in Plugins card shows manifest.json and BasePlugin code examples
• Verify Secrets Management card shows secrets.json example with Docker/bare metal paths
• Verify Example API Configurations card shows Google Books and Open Library configs
• Verify hint tooltips appear on the new cards
• Verify examples/plugins/example-logger/ contains working manifest.json and layer.py

Closes #203

[bucket-agent]

🔍 Vibe Check Review

Context

Documentation-only PR adding in-app plugin system help, an example logger plugin, a standalone plugins README, and new hint entries for plugin-related tooltips. Addresses issue #203.

Codebase Patterns I Verified

• BasePlugin interface (plugin_loader.py:47-103 on PR branch): setup(), can_process(), process(), teardown() — matches docs exactly
• Timeout: DEFAULT_PLUGIN_TIMEOUT = 30 — matches docs claim of "30s timeout"
• Confidence weight: source_weight = 60 in plugin_loader.py:335 — matches README claim of "60"
• Auto-disable threshold: AUTO_DISABLE_THRESHOLD = 5 in plugins.py:29 — matches docs claim of "5 consecutive failures"
• Hints pattern: Existing hints in hints.py use flat dict keys with descriptive strings — new entries match
• Template pattern: Existing plugins_settings.html uses Jinja2 {{"{{"}} escaping for literal braces — new cards match

✅ Good

• All factual claims (timeout, weight, failure threshold, BasePlugin methods) verified against actual code
• Example plugin is minimal and correct — good template for users
• README covers manifest fields, interface methods, behavior, and config comprehensively
• Secrets management card is a nice touch — separating keys from config is a common user confusion point
• CHANGELOG and version bump present and correct

🚨 Issues Found

Severity	Location	Exact Code Quote	Issue	Fix
MEDIUM	templates/plugins_settings.html:182	{{"{{"}}title{{"}}"}}}+inauthor:	Extra } in Google Books URL template. Renders as {{title}}} (three closing braces) instead of {{title}}. Users copying this example will get a broken template variable.	Remove the extra } — change {{"}}"}}} to {{"}}"}}}... actually, change {{"}}"}}}+inauthor: to {{"}}"}}+inauthor:

📋 Scope Verification

Issue	Problem	Addressed?	Notes
#203	Plugin system poorly documented/discoverable, unclear secrets, no real-world examples	✅	In-app help cards, example plugin, README, secrets docs, API config examples all added

Scope Status: SCOPE_OK

📝 Documentation Check

• CHANGELOG.md: ✅ Updated
• README.md: ✅ Version badge updated

Minor Notes (non-blocking)

• Two hint keys added to hints.py (custom_api_sources, plugin_health) are not referenced in any template. Not a bug — they may be intended for other UI locations — but worth confirming they're needed.

🎯 Verdict

COMMENT — The extra } in the Google Books URL example (line 182) will show users a broken template variable if they copy it. It's a cosmetic docs issue, not a code bug, so not blocking — but worth fixing before merge since the whole point of this PR is to help users get configs right.

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_{🤖 Ruthless review by vibe-check}

[bucket-agent]

🔍 Vibe Check Review

Context

Documentation PR adding in-app plugin guides, example plugin, secrets management docs, and API configuration walkthroughs for the existing plugin system (added in PRs #195-197).

Codebase Patterns I Verified

• Plugin system exists: library_manager/plugin_loader.py with BasePlugin class added in PR #197 (merged)
• from library_manager.plugin_loader import BasePlugin - correct import path, verified in PR #197 diff
• 30-second timeout - DEFAULT_PLUGIN_TIMEOUT = 30 confirmed in plugin_loader.py
• 5 consecutive failures auto-disable - AUTO_DISABLE_THRESHOLD = 5 confirmed in PR #196
• Confidence weight 60 - source_weight = 60 confirmed in plugin_loader.py (PR #197 line 448)
• default_order 35 - confirmed as default in both manifest validation and PluginInfo dataclass
• Hints pattern - new entries follow existing dict-based pattern with section comments, matching hints.py style exactly
• secrets.json - referenced in app.py and config.py (confirmed via grep)

✅ Good

• All documented claims are factually accurate against the implemented code
• Example plugin is clean, minimal, and correctly demonstrates the full BasePlugin interface
• manifest.json field table is comprehensive and matches the actual validation logic in plugin_loader.py
• Secrets management section correctly distinguishes Docker vs bare metal paths
• Google Books and Open Library API configs use correct endpoint URLs and JSONPath syntax
• Hint entries are well-written and consistent with existing hint style
• CHANGELOG and version bump are correct

🚨 Issues Found

No issues found.

📋 Scope Verification

Issue	Problem	Addressed?	Notes
#203	Plugin system poorly documented, unclear secrets management, no examples	✅	In-app guide, example plugin in examples/plugins/, secrets card, API config walkthroughs, hint tooltips - all deliverables covered

Scope Status: SCOPE_OK

📝 Documentation Check

• CHANGELOG.md: ✅ Updated (beta.145 entry)
• README.md: ✅ Version badge updated

🎯 Verdict

APPROVE - Clean docs PR. All factual claims verified against the actual plugin implementation. Ships useful documentation and a working example plugin.