## Context
One for Database Connections - allow a user to view the root blocking
queries
Adds an additional filter button here that toggles the view
<img width="738" height="142" alt="image"
src="https://github.com/user-attachments/assets/9fea17ba-c6f6-419d-8847-47dba67fc00a"
/>
When toggled, will render a list of the _root_ blocking queries - these
are queries that are at the end of the blocking chain (or otherwise the
problematic ones causing other queries to be blocked)
<img width="964" height="420" alt="image"
src="https://github.com/user-attachments/assets/5300f523-6abe-49b6-92d0-7e16bbddd291"
/>
Within this view - you can expand the row to view the blocking chain
<img width="950" height="335" alt="image"
src="https://github.com/user-attachments/assets/bb07095a-3841-4db6-8959-ac2bb264ebf6"
/>
## Other changes involved
- Realised that "Top blocker" overview metric card logic is incorrect
- Was previously naively checking the length of the `blocked_by` array,
but it should be consider the nested chain length instead, so this PR
fixes that
<img width="364" height="108" alt="image"
src="https://github.com/user-attachments/assets/89beccef-f6f0-43d1-9dcf-fc35958b09e5"
/>
- Clicking the PID if highlighted on a metric card will not scroll to
the PID if it's already selected. This PR fixes that
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added a **Root blockers** view to highlight sessions that block
others, with expandable blocking chains revealing related waiting
activity.
* **Bug Fixes**
* Updated blocking metrics to use **transitive** blocker counts and
improved cycle protection and behavior when activity records are
missing.
* The blockers view now consistently affects state/application/role
quantities, and **reset filters** clears the view.
* **Refactor / UI**
* Improved the sessions table with grouped/nested rows, clearer waiting
indicators, and more consistent expand/collapse behavior.
* **Tests**
* Expanded coverage for blocking/waiting chain traversal and branching
scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
## Context
As per PR title - no functional / visual changes, just some code clean
up / refactor + adding unit tests
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added database connection metrics covering active, blocked, and
idle-in-transaction queries.
* Enhanced insights for the longest-running query and the top blocker
(most queries blocked), including warning indicators based on duration
thresholds.
* **Bug Fixes**
* Improved consistency and accuracy of database-activity calculations in
the connection overview.
* **Refactor**
* Centralized metric derivation so the UI uses the same computed logic
everywhere.
* **Tests**
* Added metric-calculation tests with controlled time to validate
multiple scenarios and warning behaviors.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
## Context
As per PR title - we're currently showing a "danger" state for the
blocked by metric card as long as there's at least query that's blocked.
This may come off as too noisy in a real database scenario hence opting
to fine tune this behaviour a little
## Changes involved
We'll now only show the "danger" state for the blocked by metric card if
any of the blocked queries are blocked for longer than 10 seconds
<img width="356" height="256" alt="image"
src="https://github.com/user-attachments/assets/e7db5d7e-749a-4c4e-b519-9433a639b0a0"
/>
Otherwise will just be a default card
<img width="359" height="266" alt="image"
src="https://github.com/user-attachments/assets/f9aad85f-8d74-4f55-a3c5-a859d46bd8c1"
/>
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **New Features**
- Added clearer blocked-query monitoring, including the longest-blocked
process and duration.
- Added interactive selection for the longest-blocked process.
- **Bug Fixes**
- Improved activity-duration tracking across active and
idle-in-transaction states.
- Blocked-query warnings now reflect duration thresholds rather than
query count alone.
- Prevented negative duration values in blocked-query metrics.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
## Context
Improving the "blocked by" visualisation for database connections - to
accommodate the situation whereby there might be a chain of blocked
process. Intention is so that users can identify whats the root process
that's blocking everything - and from there decide if they want to
terminate the process or not.
Also brings `ActivityRow` out into its separate file since `Activity` is
getting big
<img width="473" height="299" alt="image"
src="https://github.com/user-attachments/assets/21d0d223-5dbd-49d5-877c-815c78cb7482"
/>
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Refactor**
* Streamlined the database activity view by separating the single-row
rendering into its own component, keeping the same end-user experience
(status badge, query/“No query”, duration warnings, blocking details,
PID copy, and actions).
* Kept “Terminate” behind confirmation prompts and preserved role-based
restrictions for when termination is available.
* **Improvements**
* Standardized how activity durations are calculated and how status
badges are styled for consistent display.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Joshen Lim