This PR backports the following commits from `main` branch to
`vscode-v1.42.x`:
- 45b9ff2
- bc8b14e

These commits contain fixes for Deep Cody

## Test plan

<!-- Required. See
https://docs-legacy.sourcegraph.com/dev/background-information/testing_principles.
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merged to main.

## Changelog

<!-- OPTIONAL; info at
https://www.notion.so/sourcegraph/Writing-a-changelog-entry-dd997f411d524caabf0d8d38a24a878c
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## Test plan

Unit tests added.

Also before this fix problem was visible e.g. in duplicated shortcut
tooltips next to the lens actions (due to property
`cody.advanced.agent.running` being incorrectly overwritten).
After this fix problem should disappear.

- Changed VS Code changelog links to `./vscode/changelod.md` to decouple
our releases from marketing blog posts. We want all in-product messaging
to point to our GitHub changelog, as we discussed with @kalanchan.
- We plan to move the changelog to the root of the repo and implement
changes necessary to maintain one changelog for multiple IDEs in a
follow up.

This reverts commit 36d23c2.

…tically tagged (#6083)

This makes several changes so we can do manually triggered insiders
builds from a release branch instead of nightly on `main`.

No changes to stable release builds in this PR.

## Test plan

This does a dry run of the insiders build and verifies that the version
tag is written to outputs:

```
$ CODY_RELEASE_DRY_RUN=true CODY_RELEASE_TYPE=insiders GITHUB_OUTPUT=/tmp/output.txt pnpm \
  -C vscode run release
$ cat /tmp/output.txt
version_tag=vscode-insiders-v1.41.1730969154
```

Testing the workflow itself we have to upload and trigger the workflow,
here's a fork with a dry run:

https://github.com/sourcegraph/cody/actions/runs/11719764387

## Changelog

- VSCode Insiders builds are now manually triggered, instead of nightly.
- VSCode Insiders builds can be triggered on branches. We intend to
produce these builds from release branches sometimes.
- VSCode Insiders builds are tagged with `vscode-insiders-vN.N.NNNN`.
This supports bisecting regressions in these builds.