feat: add channel list, view, and delete commands

[NickJosevski]

What

Adds three new subcommands to octopus channel:

• list — list channels for a project, with --partial-name client-side filtering. Accepts the project as a positional arg or via -p/--project.
• view — view a single channel by name, ID, or slug. Resolves the lifecycle name for display and exposes the richer channel fields (version rule counts, Git reference/resource rule counts, tenant tags, custom field definitions, and ephemeral-environment settings). Supports --web.
• delete — delete a channel by name, ID, or slug. Includes a confirmation prompt in interactive mode and a -y/--confirm flag for automation.

All three support the standard table/json/basic output formats.

Notable details

• Config-as-Code safety: delete surfaces a warning in interactive mode when the project is version-controlled, since the server does not guard against deleting a channel referenced by OCL deployments.
• Name/ID resolution: view and delete try a direct GetByID first, then fall back to a project-scoped channel lookup when given a name or slug. delete verifies the resolved channel actually belongs to the named project before deleting.

Heads-up: view/create asymmetry

view deliberately surfaces fields that the existing channel create command does not yet support — version rules, Git reference/resource rules, tenant tag scoping, and ephemeral-environment settings. This is a read-only display only; it does not add any write/edit capability for those fields. Reviewers should expect users to ask "why can I see these but not set them via CLI?", which would invite a follow-up to extend create (and possibly add update). Flagging so the scope of this PR is clear: it adds list/view/delete, not richer channel authoring.

Live testing

Smoke-tested all three commands end-to-end against a local Octopus instance:

• list — table/json/basic, positional-arg and -p flag, --partial-name filter ✅
• view — by name, ID, and slug; table/json/basic ✅
• delete — by name with -y ✅; deleting the default channel surfaces the server's You cannot delete the default channel. cleanly ✅; non-existent channel returns no channel found with name of <x> ✅
• CaC warning — verified against a real version-controlled project (file://-backed, IsVersionControlled: true): the warning shows in interactive mode before both a successful delete and a default-channel rejection, and is correctly suppressed in --no-prompt automation mode ✅

Two findings:

1. Fixed in this PR — viewing the default channel rendered an empty Lifecycle: () line, because the server returns a null LifecycleId (the default channel inherits the project lifecycle). Now displays Inherited from project, with a regression test.
2. Known limitation (not fixed here) — the live server returns a Slug field on channels, but go-octopusdeploy v2.108.0's channels.Channel struct does not expose it, so view/list cannot show channel slugs. Surfacing slugs needs an SDK bump; out of scope for this PR.

Tests

Unit tests for each command covering automation mode, interactive mode, name-lookup fallback, output formats, the CaC-deletion warning, and the inherited-lifecycle default-channel case.

ok  github.com/OctopusDeploy/cli/pkg/cmd/channel/delete
ok  github.com/OctopusDeploy/cli/pkg/cmd/channel/list
ok  github.com/OctopusDeploy/cli/pkg/cmd/channel/view

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