[ld2420] add missing docs and add docs for startup_delay

[jharris4]

Description

Related issue (if applicable): fixes

Pull request in esphome with YAML changes (if applicable):

• esphome/esphome#

Checklist

• I am merging into next because this is new documentation that has a matching pull-request in esphome as linked above.
  or

• I am merging into current because this is a fix, change and/or adjustment in the current documentation and is not for a new component or feature.

• Link added in /src/content/docs/components/index.mdx when creating new documents for new components or cookbook.

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[coderabbitai]

Walkthrough

Updated the ld2420 platform configuration documentation by replacing a single required entry with three documented optional configuration parameters: uart_id, id, and startup_delay (with a default value of zero).

Changes

Cohort / File(s)	Summary
Configuration Documentation src/content/docs/components/sensor/ld2420.mdx	Updated ld2420 platform configuration documentation to document three optional fields: uart_id, id, and startup_delay, replacing previous single required entry.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Suggested labels

current

Suggested reviewers

• nagyrobi
• clydebarrow

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main changes: adding missing documentation and documenting the startup_delay parameter for the ld2420 component.
Description check	✅ Passed	The description is a documentation template that is related to the changeset, referencing the component being documented and merge guidelines, though it uses placeholder text.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

src/content/docs/components/sensor/ld2420.mdx (1)

118-118: Clarify startup_delay default with an explicit time unit.

startup_delay is typed as [Time], so “defaults to zero” is slightly ambiguous. Consider using Defaults to \0s`` for consistency and clarity.

✏️ Suggested wording tweak

-- **startup_delay** (*Optional*, [Time](/guides/configuration-types#time)): An optional startup delay - defaults to zero.
+- **startup_delay** (*Optional*, [Time](/guides/configuration-types#time)): Optional startup delay before initialization. Defaults to `0s`.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/content/docs/components/sensor/ld2420.mdx` at line 118, The doc line for
the config field startup_delay is ambiguous because it omits a time unit; update
the description for startup_delay (in the sensor component docs) to explicitly
show the time unit, e.g., "Defaults to `0s`" or similar so it reads:
startup_delay (Optional, [Time]): An optional startup delay — defaults to 0s;
keep the [Time] type reference and formatting consistent with other Time
defaults.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/content/docs/components/sensor/ld2420.mdx`:
- Line 118: The doc line for the config field startup_delay is ambiguous because
it omits a time unit; update the description for startup_delay (in the sensor
component docs) to explicitly show the time unit, e.g., "Defaults to `0s`" or
similar so it reads: startup_delay (Optional, [Time]): An optional startup delay
— defaults to 0s; keep the [Time] type reference and formatting consistent with
other Time defaults.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 1c1e8b14-05e0-4e40-9a8e-2a7d79562ba9

📥 Commits

Reviewing files that changed from the base of the PR and between 1b005da and 60397e3.

📒 Files selected for processing (1)

• src/content/docs/components/sensor/ld2420.mdx

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